Lithographic printing plate precursor, method for producing lithographic printing plate, polymer particle, and composition

ABSTRACT

Provided are a lithographic printing plate precursor having an image-recording layer on a hydrophilic support, in which the image-recording layer includes a polymer particle including an addition polymerization-type resin having a hydrophilic structure and a crosslinking structure, a method for producing a lithographic printing plate in which the lithographic printing plate precursor is used, a polymer particle including an addition polymerization-type resin having a hydrophilic structure and a crosslinking structure, and a composition including the polymer particle.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of International Application No.PCT/JP2018/017814 filed on May 8, 2018, which claims priority toJapanese Patent Application No. 2017-108002 filed on May 31, 2017 andJapanese Patent Application No. 2017-210126 filed on Oct. 31, 2017. Theentire contents of these applications are incorporated herein byreference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present disclosure relates to a lithographic printing plateprecursor, a method for producing a lithographic printing plate, apolymer particle, and a composition.

2. Description of the Related Art

Generally, a lithographic printing plate consists of a lipophilic imagearea that receives ink in a printing process and a hydrophilic non-imagearea that receives dampening water. Lithographic printing is a method inwhich the properties of water and oil-based ink that repel each otherare used, the lipophilic image area of the lithographic printing plateis used as an ink-receiving portion, the hydrophilic non-image area isused as a dampening water-receiving portion (non-ink-receiving portion),a difference in the adhesive property of ink is caused on the surface ofthe lithographic printing plate, the ink is absorbed only in the imagearea, and then the ink is transferred to a body to be printed such aspaper, thereby carrying out printing.

In order to produce this lithographic printing plate, in the relatedart, a lithographic printing plate precursor (PS plate) formed byproviding a lipophilic photosensitive resin layer (image-recordinglayer) on a hydrophilic support has been broadly used. Generally, aplate is made using a method in which a lithographic printing plateprecursor is exposed to light through an original drawing such as a lithfilm, a portion which is to be an image area of the image-recordinglayer is left, the other unnecessary portion of the image-recordinglayer is dissolved and removed using an alkaline developer or an organicsolvent, and a hydrophilic surface of a support is exposed, therebyforming a non-image area and a lithographic printing plate is obtained.

In addition, in response to the intensifying interest in the globalenvironment, an environmental issue of waste liquid generated by wetprocesses such as a development process has gathered more attention.

Regarding the above-described environmental issue, an attempt is made tosimplify development or plate production or remove processes. As one ofsimple production methods, a method called “on-machine development” isbeing carried out. That is, in the method, after being exposed, alithographic printing plate precursor is immediately mounted in aprinter without being developed as in the related art, and anunnecessary portion of the image-recording layer is removed in aninitial phase of an ordinary printing step.

As lithographic printing plate precursors of the related art,lithographic printing plate precursors described in JP2003-025750A andJP2004-525420A are exemplified.

JP2003-025750A describes an image-forming material having animage-forming layer containing at least one kind of thermally fusiblepolymer particle on a support, in which the polymer particle is anactive methylene group-containing polymer latex.

JP2004-525420A describes an image-forming element including a base body;and a thermosensitive image-forming composition that coats a surface ofthe base body, in which the thermosensitive image-forming compositioncontains a hydrophobic polymer backbone and a graft copolymer having aplurality of pendant groups represented by Formula

-Q-W—Y

(in the formula, Q is a bifunctional linking group; W is selected fromthe group consisting of a hydrophilic segment and a hydrophobic segment;Y is selected from the group consisting of a hydrophilic segment and ahydrophobic segment, here, in a case in which W is a hydrophilicsegment, Y is selected from the group consisting of a hydrophilicsegment and a hydrophobic segment, and, furthermore, in a case in whichW is hydrophobic, the Y is a hydrophilic segment).

SUMMARY OF THE INVENTION

As lithographic printing plates, there is a demand for lithographicprinting plates being excellent in terms of the number of printableplates (hereinafter, also referred to as “printing resistance”).

Particularly, in recent years, as ink for printing, there is a case inwhich ink that cures by irradiation with ultraviolet (UV) rays (alsoreferred to as “ultraviolet-curable ink”) is used.

The ultraviolet-curable ink has the following advantages. Theultraviolet-curable ink can be instantly dried and is thus highlyproductive, generally contains a small content of a solvent or nosolvent and thus easily reduces environmental contamination, and iscapable of forming an image without being dried by heat or by beingdried by heat for a short period of time and is thus applicable to abroad range of printing subjects.

Therefore, lithographic printing plates capable of providinglithographic printing plates having excellent printing resistance in thecase of using the ultraviolet-curable ink are considered to be extremelyuseful in terms of industries.

The present inventors carried out intensive studies and consequentlyfound that, regarding the lithographic printing plate precursor ofJP2003-025750A or JP2004-525420A, there is a problem in that,particularly in the case of using the ultraviolet-curable ink as ink,the printing resistance of a lithographic printing plate to be obtainedis not sufficient.

An object that an embodiment of the present invention attempts to attainis to provide a lithographic printing plate precursor from which alithographic printing plate having excellent printing resistance can beobtained even in the case of using an ultraviolet-curable ink.

In addition, an object that another embodiment of the present inventionattempts to attain is to provide a method for producing a lithographicprinting plate having excellent printing resistance even in the case ofusing an ultraviolet-curable ink.

An object that still another embodiment of the present inventionattempts to attain is to provide a new polymer particle and acomposition including the polymer particle.

Means for achieving the above-described objects includes the followingaspects.

<1> A lithographic printing plate precursor comprising: animage-recording layer on a hydrophilic support, in which theimage-recording layer includes a polymer particle including an additionpolymerization-type resin having a hydrophilic structure and acrosslinking structure.

<2> The lithographic printing plate precursor according to <1>, in whichthe addition polymerization-type resin has an ionic group or an acidradical as the hydrophilic structure.

<3> The lithographic printing plate precursor according to <1> or <2>,in which the addition polymerization-type resin has a sulfonate group ora sulfonic acid group as the hydrophilic structure.

<4> The lithographic printing plate precursor according to any one of<1> to <3>, in which the addition polymerization-type resin has apolyalkylene oxide structure as the hydrophilic structure.

<5> The lithographic printing plate precursor according to any one of<1> to <4>, in which the addition polymerization-type resin has a grouprepresented by Formula Z as a group having the hydrophilic structure.

-Q-W—Y  Formula Z

In Formula Z, Q represents a divalent linking group, W represents adivalent group having a hydrophilic structure or a divalent group havinga hydrophobic structure, Y represents a monovalent group having ahydrophilic structure or a monovalent group having a hydrophobicstructure; here, any of W and Y has a hydrophilic structure.

<6> The lithographic printing plate precursor according to any one of<1> to <5>, in which the crosslinking structure includes at least oneconstituent unit selected from the group consisting of constituent unitsrepresented by BR-1 to BR-16.

In the structure, R^(BR) each independently represent a hydrogen atom ora methyl group, and n represents an integer of 1 to 20.

<7> The lithographic printing plate precursor according to any one of<1> to <6>, in which the image-recording layer further includes aninfrared absorber, a polymerization initiator, and a polymerizablecompound.

<8> The lithographic printing plate precursor according to any one of<1> to <7>, in which the image-recording layer further includes a binderpolymer.

<9> The lithographic printing plate precursor according to any one of<1> to <8>, further comprising: a protective layer on theimage-recording layer.

<10> The lithographic printing plate precursor according to <9>, inwhich the protective layer includes an inorganic lamellar compound.

<11> The lithographic printing plate precursor according to any one of<1> to <10>, in which a non-exposed portion of the image-recording layercan be removed by at least any of dampening water or printing ink.

<12> A method for producing a lithographic printing plate comprising:

an exposure step of exposing the lithographic printing plate precursoraccording to any one of <1> to <11> in an image shape and forming anexposed portion and a non-exposed portion; and

an on-machine development step of removing the non-exposed portion bysupplying at least one of printing ink or dampening water.

<13> A polymer particle comprising: an addition polymerization-typeresin having a hydrophilic structure and a crosslinking structure.

<14> The polymer particle according to <13>, in which the additionpolymerization-type resin has an ionic group or an acid radical as thehydrophilic structure.

<15> The polymer particle according to <13> or <14>, in which theaddition polymerization-type resin has a sulfonate group or a sulfonicacid group as the hydrophilic structure.

<16> The polymer particle according to any one of <13> to <15>, in whichthe addition polymerization-type resin has a polyalkylene oxidestructure as the hydrophilic structure.

<17> The polymer particle according to any one of <13> to <16>, in whichthe addition polymerization-type resin has a group represented byFormula Z as a group having the hydrophilic structure.

-Q-W—Y  Formula Z

In Formula Z, Q represents a divalent linking group, W represents adivalent group having a hydrophilic structure or a divalent group havinga hydrophobic structure, Y represents a monovalent group having ahydrophilic structure or a monovalent group having a hydrophobicstructure; here, any of W and Y has a hydrophilic structure.

<18> The polymer particle according to any one of <13> to <17>, in whichthe crosslinking structure includes at least one constituent unitselected from the group consisting of constituent units represented byBR-1 to BR-16.

In the structure, R^(BR) each independently represent a hydrogen atom ora methyl group, and n represents an integer of 1 to 20.

<19> A composition comprising: the polymer particle according to any oneof <13> to <18>.

<20> The composition according to <19>, further comprising: an infraredabsorber; a polymerization initiator; and a polymerizable compound.

<21> A method for producing a lithographic printing plate comprising:

an exposure step of exposing the lithographic printing plate precursoraccording to any one of <1> to <11> in an image shape and forming anexposed portion and a non-exposed portion; and

a development step of removing the non-exposed portion by supplying adeveloper having a pH of 2 or higher and 11 or lower.

According to the embodiment of the present invention, it is possible toprovide a lithographic printing plate precursor from which alithographic printing plate having excellent printing resistance can beobtained even in the case of using an ultraviolet-curable ink.

In addition, according to the another embodiment of the presentinvention, it is possible to provide a method for producing alithographic printing plate having excellent printing resistance even inthe case of using an ultraviolet-curable ink.

According to the still another embodiment of the present invention, itis possible to provide a new polymer particle and a resin compositionincluding the polymer particle.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, the contents of the present disclosure will be described indetail. Constituent requirements mentioned below will be described onthe basis of typical embodiments of the present disclosure, but thepresent disclosure is not limited to such embodiments.

Meanwhile, in the present specification, a numerical range expressedusing “to” includes numerical values described before and after “to” asthe lower limit value and the upper limit value.

In addition, in the present specification, a group (atomic group) thatis not expressed whether the group is substituted or not substitutedrefers to both a group not having a substituent and a group having asubstituent. For example, an “alkyl group” refers not only to an alkylgroup not having a substituent (unsubstituted alkyl group) but also toan alkyl group having a substituent (substituted alkyl group).

In the present specification, “(meth)acryl” is an expression used with aconcept of including both acryl and methacryl, and “(meth)acryloyl” isan expression used with a concept of including both acryloyl andmethacryloyl.

In addition, the term “step” in the present specification refers notonly to an independent step but also a step that cannot be clearlydifferentiated from other steps as long as the intended purpose of thestep is achieved. In addition, in the present disclosure, “% by mass”and “% by weight” have the same meaning, and “parts by mass” and “partsby weight” have the same meaning.

Furthermore, in the present disclosure, a combination of two or morepreferred aspects is a more preferred aspect.

In addition, unless particularly otherwise described, the weight-averagemolecular weight (Mw) and the number average molecular weight (Mn) inthe present disclosure refer to a molecular weight that is detectedusing a gel permeation chromatography (GPC) analyzer in which columns ofTSKgel GMHxL, TSKgel G4000HxL, and TSKgel G2000HxL (all are trade namesmanufactured by Tosoh Corporation) are used, solvent tetrahydrofuran(THF), and a differential refractometer and is converted usingpolystyrene as a standard substance.

In the present specification, the term “lithographic printing plateprecursor” refers not only to a lithographic printing plate precursorbut also to a key plate precursor. In addition, the term “lithographicprinting plate” refers not only to a lithographic printing plateproduced by carrying out operations such as exposure and development asnecessary on the lithographic printing plate precursor but also to a keyplate. In the case of the key plate precursor, the operations such asexposure and development are not necessarily required. Meanwhile, thekey plate refers to a lithographic printing plate precursor intended tobe attached to a plate cylinder that is not used in a case in whichmonochromatic or dichromatic printing is carried out on a part of paperduring, for example, color newspaper printing.

In addition, in the present specification, “*” in a chemical structuralformula represents a bonding position with other structures.

Hereinafter, the present disclosure will be described in detail.

(Lithographic Printing Plate Precursor)

A lithographic printing plate precursor according to an embodiment ofthe present disclosure has an image-recording layer on a hydrophilicsupport, the image-recording layer includes a polymer particle includingan addition polymerization-type resin having a hydrophilic structure anda crosslinking structure.

In addition, the lithographic printing plate precursor according to theembodiment of the present disclosure can be preferably used as anon-machine development-type lithographic printing plate precursor.

As a result of intensive studies, the present inventors found that, in acase in which the above-described constitution is provided, it ispossible to provide a lithographic printing plate precursor from which alithographic printing plate having printing resistance (hereinafter,also referred to as UV printing resistance) that is excellent even inthe case of using an ultraviolet-curable ink can be obtained.

A detailed mechanism for the obtainment of the above-described effect isnot clear, but is assumed as described below.

It is considered that the polymer particle including an additionpolymerization-type resin having a crosslinking structure increases thehardness of the polymer particle and the addition polymerization-typeresin having a hydrophilic structure improves the dispersibility of thepolymer particle, facilitates the dispersion of the polymer particle inan almost uniform state in the image-recording layer, improves thestrength of the entire image-recording layer, and improves printingresistance even in the case of using ultraviolet-curable ink that ismore likely to deteriorate plates than other inks.

In addition, it is considered that the polymer particle that is used inthe present disclosure has a hydrophilic structure, whereby the affinityto ink or dampening water improves and it is easy to obtain alithographic printing plate precursor that is excellent in terms ofon-machine developability and an on-machine development scum suppressionproperty.

<Image-Recording Layer>

The lithographic printing plate precursor of the embodiment of thepresent disclosure has an image-recording layer including the polymerparticle.

The image-recording layer that is used in the present disclosure ispreferably a negative-type image-recording layer.

From the viewpoint of printing resistance and photosensitivity, theimage-recording layer in the present disclosure is preferably any aspectof a first aspect and a second aspect described below.

The first aspect contains the polymer particle, an infrared absorber, apolymerization initiator, and a polymerizable compound.

The second aspect contains the polymer particle, an infrared absorber,and a hydrophobic thermoplastic polymer particle.

From the viewpoint of printing resistance, particularly UV printingresistance, the image-recording layer that is used in the presentdisclosure preferably further contains a binder polymer in the firstaspect.

In addition, from the viewpoint of on-machine developability, theimage-recording layer that is used in the present disclosure may furthercontain a hydrophobic thermoplastic polymer particle in the firstaspect.

From the viewpoint of on-machine developability, in the lithographicprinting plate precursor of the embodiment of the present disclosure, anon-exposed portion of the image-recording layer preferably can beremoved by at least any of dampening water or printing ink.

Hereinafter, individual components that are included in theimage-recording layer will be described in detail.

—Polymer Particle—

The image-recording layer in the lithographic printing plate precursoraccording to the embodiment of the present disclosure includes a polymerparticle including an addition polymerization-type resin having ahydrophilic structure and a crosslinking structure.

From the viewpoint of UV printing resistance and on-machinedevelopability, the polymer particle preferably includes 80% by mass ormore of the addition polymerization-type resin, more preferably includes90% by mass or more of the addition polymerization-type resin, stillmore preferably includes 95% by mass or more of the additionpolymerization-type resin, and is particularly preferably a particleconsisting of the addition polymerization-type resin.

From the viewpoint of UV printing resistance and production feasibility,the addition polymerization-type resin is preferably a resin obtained bypolymerizing an ethylenically unsaturated compound and more preferably aresin obtained by copolymerizing a polyfunctional ethylenicallyunsaturated compound and a monofunctional ethylenically unsaturatedcompound.

The addition polymerization-type resin may have only one kind of thehydrophilic structure and only one kind of the crosslinking structure ormay have two or more kinds of any one or both of the hydrophilicstructure and the crosslinking structure.

˜Hydrophilic Structure˜

The addition polymerization-type resin has at least a hydrophilicstructure.

From the viewpoint of UV printing resistance, on-machine developability,an on-machine development scum suppression property, and the dispersionstability of particles, particularly, the dispersion stability in water,the addition polymerization-type resin preferably has, as thehydrophilic structure, an ionic group or an acid radical and morepreferably has an ionic group.

In addition, from the viewpoint of UV printing resistance, on-machinedevelopability, an on-machine development scum suppression property, andthe dispersion stability of particles, particularly, the dispersionstability in water, the addition polymerization-type resin morepreferably has, as the hydrophilic structure, a sulfonate group (a saltof sulfonic acid group) or a sulfonic acid group.

From the viewpoint of UV printing resistance, on-machine developability,an on-machine development scum suppression property, and the dispersionstability of particles, particularly, the dispersion stability in anorganic solvent, the addition polymerization-type resin preferably has,as the hydrophilic structure, a polyalkylene oxide structure or apolyester structure and more preferably has a polyalkylene oxidestructure.

Furthermore, from the viewpoint of UV printing resistance, on-machinedevelopability, an on-machine development scum suppression property, andthe dispersion stability of particles, the addition polymerization-typeresin particularly preferably has, as the hydrophilic structure, anionic group or an acid radical and a polyalkylene oxide structure.

From the viewpoint of on-machine developability, an on-machinedevelopment scum suppression property, and the dispersion stability ofparticles, as the acid radical, a sulfonate group, a carboxylate group,a phosphate group, or a sulfuric acid monoester group are preferablyexemplified, a sulfonate group or a carboxylate group is more preferablyexemplified, and a sulfonate group is particularly preferablyexemplified.

From the viewpoint of UV printing resistance, on-machine developability,an on-machine development scum suppression property, and the dispersionstability of particles, as the ionic group, a group generating an anionby disassociating a counterion (anionic group) is preferred, a salt ofan acid radical is more preferably exemplified, a sulfonate group, acarboxylate group, or a sulfonic acid monoester salt group is still morepreferably exemplified, and a sulfonate group is particularly preferablyexemplified.

A counter cation in the salt of the acid radical may be an inorganiccation or an organic cation, but is preferably an inorganic cation. Inaddition, the counter cation may be not only a monovalent cation butalso a polyvalent cation, but is preferably a monovalent cation.

As the inorganic cation, an alkali metal ion or an alkali earth metalion is more preferred, an alkali metal ion is more preferred, and alithium ion, a sodium ion, or a potassium ion is particularly preferred.

As the organic cation, a quaternary ammonium cation, a cation obtainedby alkylating a nitrogen atom in an aromatic nitrogen-containingheterocycle, and the like are exemplified.

As the quaternary ammonium cation, a tetramethylammonium cation, atetraethylammonium cation, and a dimethylbenzylammonium cation areexemplified, and, as the cation obtained by alkylating a nitrogen atomin an aromatic nitrogen-containing heterocycle, a pyridinium cation isexemplified.

Among these, the counter cation is preferably an alkali metal ion or aquaternary ammonium cation and particularly preferably an alkali metalion.

From the viewpoint of UV printing resistance, on-machine developability,an on-machine development scum suppression property, and the dispersionstability of particles, the addition polymerization-type resinpreferably has a constituent unit represented by Formula A-1 or FormulaA-2.

In Formula A-1 and Formula A-2, X¹ represents O or NR³, L¹ represents adivalent linking group having 1 to 20 carbon atoms, R¹ represents anionic group or an acid radical, R² represents a hydrogen atom or amethyl group, and R³ represents a hydrogen atom, an alkyl group, or anaryl group.

X¹ is preferably O.

L¹ is preferably a divalent linking group having 2 to 10 carbon atoms,more preferably a divalent linking group having 2 to 8 carbon atoms,still more preferably an alkylene group having 2 to 8 carbon atoms, andparticularly preferably an alkylene group having 2 to 5 carbon atoms.

The divalent linking group is preferably an alkylene group or a groupobtained by bonding one or more alkylene groups and one or more of atleast one kind of structure selected from the group consisting of anether bond and an ester bond, and more preferably an alkylene group.

R³ is preferably a hydrogen atom, an alkyl group having 1 to 4 carbonatoms, or a phenyl group and more preferably a hydrogen atom.

From the viewpoint of the dispersion stability of particles,particularly, the dispersion stability of an organic solvent, thepolyalkylene oxide structure is preferably a polyethylene oxidestructure, a polypropylene oxide structure, or a poly(ethyleneoxide/propylene oxide) structure.

From the viewpoint of the dispersion stability of particles,particularly, the dispersion stability of an organic solvent, the numberof the alkylene oxide structures in the polyalkylene oxide structure ispreferably 2 or more, more preferably 5 or more, still more preferably 5to 200, and particularly preferably 8 to 150.

The polyester structure is not particularly limited, but a ring-openingpolymer chain of a lactone and a polycondensation chain ofhydroxycarboxylic acid are preferably exemplified.

From the viewpoint of the dispersion stability of particles,particularly, the dispersion stability of an organic solvent, the numberof hydroxycarboxylic acid structures (lactone structures) in thepolyester structure is preferably 2 or more, more preferably 2 to 20,still more preferably 2 to 10, and particularly preferably 4 to 10.

From the viewpoint of UV printing resistance, on-machine developability,an on-machine development scum suppression property, and the dispersionstability of particles, the addition polymerization-type resinpreferably has a constituent unit represented by Formula A-3 or FormulaA-4 and more preferably has a constituent unit represented by FormulaA-3.

In Formula A-3 and Formula A-4, L² represents an ethylene group or apropylene group, L³ represents an alkylene group having 2 to 10 carbonatoms, L⁴ represents an alkylene group having 1 to 10 carbon atoms, R⁴and R⁶ each independently represent a hydrogen atom, an alkyl group, oran aryl group, R⁵ and R⁷ each independently represent a hydrogen atom ora methyl group, m1 represents an integer of 2 to 200, and m2 representsan integer of 2 to 20.

L² is preferably an ethylene group or a 1,2-propylene group.

L³ is preferably an alkylene group having 2 to 8 carbon atoms, morepreferably an alkylene group having 2 to 4 carbon atoms, and still morepreferably an ethylene group.

L⁴ is preferably an alkylene group having 2 to 8 carbon atoms, morepreferably an alkylene group having 3 to 8 carbon atoms, and still morepreferably an alkylene group having 4 to 6 carbon atoms.

R⁴ and R⁶ each are independently preferably a hydrogen atom, an alkylgroup having 1 to 4 carbon atoms, or a phenyl group, more preferably ahydrogen atom or an alkyl group having 1 to 4 carbon atoms, and stillmore preferably a hydrogen atom or a methyl group.

m1 is preferably an integer of 5 to 200 and more preferably an integerof 8 to 150.

m2 is preferably an integer of 2 to 10 and more preferably an integer of4 to 10.

From the viewpoint of UV printing resistance, on-machine developability,an on-machine development scum suppression property, and the dispersionstability of particles, the addition polymerization-type resinparticularly preferably has the constituent unit represented by FormulaA-1 or Formula A-2 and the constituent unit represented by Formula A-3or Formula A-4 and most preferably has the constituent unit representedby Formula A-1 or Formula A-2 and the constituent unit represented byFormula A-3.

From the viewpoint of on-machine developability, an on-machinedevelopment scum suppression property, and the dispersion stability ofparticles, the addition polymerization-type resin preferably has, as agroup having the hydrophilic structure, a group represented by FormulaZ.

-Q-W—Y  Formula Z

In Formula Z, Q represents a divalent linking group, W represents adivalent group having a hydrophilic structure or a divalent group havinga hydrophobic structure, Y represents a monovalent group having ahydrophilic structure or a monovalent group having a hydrophobicstructure; here, any of W and Y has a hydrophilic structure.

Q is preferably a divalent linking group having 1 to 20 carbon atoms andmore preferably a divalent linking group having 1 to 10 carbon atoms.

In addition, Q is preferably an alkylene group, an arylene group, anester bond, an amide bond, or a group obtained by combining two or moregroups or bonds described above and more preferably a phenylene group,an ester bond, or an amide bond.

The divalent group having a hydrophilic structure as W is preferably apolyalkyleneoxy group or a group having —CH₂CH₂NR^(W)— bonding to oneterminal of a polyalkyleneoxy group. Meanwhile, R^(W) represents ahydrogen atom or an alkyl group.

The divalent group having a hydrophobic structure as W is preferably—R^(WA)—, —O—R^(WA)—O—, —R^(W)N—R^(WA)—NR^(W)—, —OOC—R^(WA)—O—, or—OOC—R^(WA)—O—. Meanwhile, R^(WA) each respectively represents a linearchain having 6 to 120 carbon atoms, a branched or cyclic alkylene group,a haloalkylene group having 6 to 120 carbon atoms, an arylene grouphaving 6 to 120 carbon atoms, an alkarylene group (a divalent groupobtained by removing one hydrogen atom from an alkylaryl group) having 6to 120 carbon atoms, or an aralkylene group having 6 to 120 carbonatoms.

The monovalent group having a hydrophilic structure as Y is preferablyOH, COOH, a polyalkyleneoxy group having a hydrogen atom or an alkylgroup at one terminal, or a group having —CH₂CH₂N(R^(W))— bonding to theother terminal of the polyalkyleneoxy group having a hydrogen atom or analkyl group at one terminal.

The monovalent group having a hydrophobic structure as Y is preferably alinear, branched, or cyclic alkyl group having 6 to 120 carbon atoms, ahaloalkyl group having 6 to 120 carbon atoms, an aryl group having 6 to120 carbon atoms, an alkaryl group (an alkylaryl group) having 6 to 120carbon atoms, an aralkyl group having 6 to 120 carbon atoms, OR^(WB),COOR^(WB), or OOCR^(WB). Meanwhile, R^(WB) represents an alkyl grouphaving 6 to 20 carbon atoms.

From the viewpoint of on-machine developability, an on-machinedevelopment scum suppression property, and the dispersion stability ofparticles, the content of a constituent unit having a hydrophilicstructure in the addition polymerization-type resin is preferably 1% bymass to 50% by mass, more preferably 5% by mass to 40% by mass, andparticularly preferably 10% by mass to 30% by mass of the total mass ofthe addition polymer-type resin.

In addition, in a case in which the hydrophilic structure is an ionicgroup, from the viewpoint of on-machine developability, an on-machinedevelopment scum suppression property, and the dispersion stability ofparticles, the content of a constituent unit having an ionic group inthe addition polymerization-type resin is preferably 1% by mass to 30%by mass, more preferably 2% by mass to 20% by mass, and particularlypreferably 4% by mass to 10% by mass of the total mass of the additionpolymerization-type resin.

˜Crosslinking Structure˜

The addition polymerization-type resin has at least a crosslinkingstructure.

The crosslinking structure is not particularly limited, but ispreferably a constituent unit formed by the polymerization of apolyfunctional ethylenically unsaturated compound.

From the viewpoint of UV printing resistance and on-machinedevelopability, the number of functional groups in the polyfunctionalethylenically unsaturated compound is preferably 2 to 15, morepreferably 3 to 10, still more preferably 4 to 10, and particularlypreferably 5 to 10.

In addition, in the case of expressing the above description in adifferent manner, from the viewpoint of UV printing resistance andon-machine developability, the crosslinking structure is preferably adifunctional to quinquedecafunctional branched unit, more preferably atrifunctional to decafunctional branched unit, still more preferably atetrafunctional to decafunctional branched unit, and particularlypreferably a pentafunctional to decafunctional branched unit.

Meanwhile, the branched unit refers to a constituent unit having abranch point (crosslinking structure).

The number of carbon atoms in the branched unit is not particularlylimited, but is preferably 8 to 100 and more preferably 8 to 70.

In addition, from the viewpoint of UV printing resistance, on-machinedevelopability, and the strength of particles, the crosslinkingstructure preferably includes at least one constituent unit selectedfrom the group consisting of constituent units represented by BR-1 toBR-16, more preferably includes at least one constituent unit selectedfrom the group consisting of constituent units represented by BR-1 toBR-10 or BR-13 to BR-16, still more preferably includes at least oneconstituent unit selected from the group consisting of constituent unitsrepresented by BR-1 to BR-7 or BR-13 to BR-16, and particularlypreferably includes the constituent unit represented by BR-1.

In the structure, R^(BR) each independently represent a hydrogen atom ora methyl group, and n represents an integer of 1 to 20.

From the viewpoint of UV printing resistance and on-machinedevelopability, the content of a constituent unit having a crosslinkingstructure in the addition polymerization-type resin is preferably 1% bymass to 50% by mass, more preferably 5% by mass to 45% by mass, stillmore preferably 10% by mass to 40% by mass, and particularly preferably10% by mass to 35% by mass of the total mass of the additionpolymer-type resin.

The addition polymerization-type resin may have a constituent unit otherthan the constituent unit having a hydrophilic structure and theconstituent unit having a crosslinking structure (additional constituentunit).

As a compound forming the additional constituent unit, monofunctionalethylenically unsaturated compounds such as a styrene compound, a(meth)acrylate compound, a (meth)acrylonitrile compound, a(meth)acrylamide compound, a vinyl halide compound, a vinyl estercompound, a vinyl ether compound, and an α-olefin compound arepreferably exemplified.

Specifically, for example, styrene, methyl methacrylate, acrylonitrile,methacrylonitrile, N,N-dimethylacrylamide, 2-hydroxyethyl acrylate,2,3-dihydroxypropyl methacrylate, 2-ethylhexyl methacrylate, acryloylmorpholine, diacetone acrylamide, N-isopropylacrylamide, cyclohexylmethacrylate, acryloxymethyl ethylene carbonate, p-t-butylstyrene,methacrylamide, and the like are more preferably exemplified.

Among these, the addition polymerization-type resin still morepreferably has at least one constituent unit selected from the groupconsisting of a constituent unit consisting of acrylonitrile, aconstituent unit consisting of methyl methacrylate, and a constituentunit consisting of styrene and particularly preferably has a constituentunit consisting of acrylonitrile.

Meanwhile, the constituent unit consisting of acrylonitrile is aconstituent unit represented by X-1, the constituent unit consisting ofmethyl methacrylate is a constituent unit represented by X-2, and theconstituent unit consisting of styrene is a constituent unit representedby X-3.

The addition polymerization-type resin may have one additionalconstituent unit, may have two or more additional constituent units, ormay not have any additional constituent unit.

From the viewpoint of UV printing resistance and on-machinedevelopability, the content of the additional constituent unit in theaddition polymerization-type resin is preferably 10% by mass to 90% bymass, more preferably 20% by mass to 85% by mass, still more preferably40% by mass to 80% by mass, and particularly preferably 50% by mass to75% by mass of the total mass of the addition polymer-type resin.

Regarding the molecular weight of the addition polymerization-typeresin, the mass average molecular weight (Mw) as a polystyreneequivalent value by a GPC method is preferably 2,000 or more, morepreferably 5,000 or more, and still more preferably 10,000 to20,000,000.

From the viewpoint of improvement in UV printing resistance, thevolume-average particle diameter of the polymer particle is preferably50 nm to 1,000 nm and more preferably 80 nm to 600 nm.

The volume-average particle diameter of the polymer particle is a valuemeasured using a laser diffraction/scattering-type particle sizedistribution analyzer LA-920 (manufactured by Horiba Ltd.).

In the present disclosure, as the polymer particle that is preferablyused, G-1 to G-21 are exemplified. Meanwhile, average particle diametersbelow are volume-average particle diameters, the contents (suffixes onthe lower right side of parentheses) of individual constituent units aremass ratios, and a suffix on the lower right side of a parenthesis ofthe polyalkyleneoxy structure or a polyhydroxycarboxylate structurerepresents the number of times of repetition, and * represents a bondingposition with other structures.

From the viewpoint of UV printing resistance and on-machinedevelopability, the content of the polymer particle in theimage-recording layer of the lithographic printing plate precursor ofthe embodiment of the present disclosure is preferably 10% by mass to90% by mass, more preferably 20% by mass to 80% by mass, still morepreferably 30% by mass to 70% by mass, and particularly preferably 35%by mass to 65% by mass of the total mass of the image-recording layer.

—Infrared Absorber—

The image-recording layer preferably includes an infrared absorber.

The infrared absorber has a function of converting absorbed infraredrays to heat and a function of migrating electrons and/or migratingenergy to a polymerization initiator described below by being excited byinfrared rays. The infrared absorber that is used in the presentdisclosure is preferably a dye having the maximum absorption at awavelength of 750 nm to 1,400 nm.

As the dye, it is possible to use a commercially available dye and awell-known dye described in publications, for example, “Dye Handbooks”(edited by the Society of Synthetic Organic Chemistry, Japan andpublished on 1970). Specific examples thereof include dyes such as anazo dye, a metal complex azo dye, a pyrazolone azo dye, a naphthoquinonedye, an anthraquinone dye, a phthalocyanine dye, a carbonium dye, aquinoneimine dye, a methine dye, a cyanine dye, a squarylium colorant, apyrylium salt, and a metal thiolate complex.

Among these dyes, as preferred dyes, a cyanine colorant, a squaryliumcolorant, a pyrylium salt, a nickel thiolate complex, and an indoleninecyanine colorant are exemplified. Furthermore, a cyanine colorant or anindolenine cyanine colorant is more preferably exemplified. Betweenthese, a cyanine colorant is particularly preferred.

Specific examples of the cyanine colorant include a compound describedin Paragraphs 0017 to 0019 of JP2001-133969A, a compound described inParagraphs 0016 to 0021 of JP2002-023360A and Paragraphs 0012 to 0037 ofJP2002-040638A, preferably a compound described in Paragraphs 0034 to0041 of JP2002-278057A and Paragraphs 0080 to 0086 of JP2008-195018A,particularly preferably a compound described in Paragraphs 0035 to 0043of JP2007-090850A, and a compound described in Paragraphs 0105 to 0113of JP2012-206495A.

In addition, it is also possible to preferably use a compound describedin Paragraphs 0008 and 0009 of JP1993-005005A (JP-H05-005005A) andParagraphs 0022 to 0025 of JP2001-222101A.

As the pigment, a compound described in Paragraphs 0072 to 0076 ofJP2008-195018A is preferred.

The infrared absorber may be used singly or two or more infraredabsorbers may be jointly used. In addition, a pigment and a dye may bejointly used as the infrared absorber.

The content of an infrared-absorber in the image-recording layer ispreferably 0.1% by mass to 10.0% by mass and more preferably 0.5% bymass to 5.0% by mass of the total mass of the image-recording layer.

—Polymerization Initiator—

The image-recording layer that is used in the present disclosurepreferably contains a polymerization initiator and more preferablycontains a polymerization initiator and a polymerizable compound.

The polymerization initiator is a compound that initiates andaccelerates the polymerization of a polymerizable compound. As thepolymerization initiator, it is possible to use a well-knownthermopolymerization initiator, a compound having a bond with a smallbond dissociation energy, a photopolymerization initiator, or the like.Specifically, radical polymerization initiators described in Paragraphs0092 to 0106 of JP2014-104631A can be used.

Among polymerization initiators, as a preferred compound, an onium saltis exemplified. Particularly, an iodonium salt and a sulfonium salt areparticularly preferably exemplified. Specific preferred compounds amongthe respective salts are the same as the compounds described inParagraphs 0104 to 0106 of JP2014-104631A.

The content of the polymerization initiator is preferably 0.1% by massto 50% by mass, more preferably 0.5% by mass to 30% by mass, andparticularly preferably 0.8% by mass to 20% by mass of the total mass ofthe image-recording layer. In a case in which the content of thepolymerization initiator is in the above-described range, a morefavorable sensitivity and a more favorable resistance of a non-imagearea to contamination during printing can be obtained.

—Polymerizable Compound—

The image-recording layer used in the present disclosure preferablycontains a polymerizable compound.

The polymerizable compound that is used in the image-recording layer maybe, for example, a radical polymerizable compound or a cationicpolymerizable compound, but is preferably an addition polymerizablecompound having at least one ethylenically unsaturated bond(ethylenically unsaturated compound). The ethylenically unsaturatedcompound is preferably a compound having at least one terminalethylenically unsaturated bond and more preferably a compound having twoor more terminal ethylenically unsaturated bonds. The polymerizablecompound may have a chemical form, for example, a monomer, a prepolymer,that is, a dimer, a trimer, or an oligomer, or a mixture thereof.

Examples of the monomer include unsaturated carboxylic acids (forexample, acrylic acid, methacrylic acid, itaconic acid, crotonic acid,isocrotonic acid, and maleic acid), esters thereof, and amides thereof.Esters of unsaturated carboxylic acids and polyvalent amine compoundsand amides of unsaturated carboxylic acids and polyhydric alcoholcompounds are preferably used. In addition, addition reaction productsbetween unsaturated carboxylic acid esters or amides having nucleophilicsubstituents such as hydroxy groups, amino groups, or mercapto groupsand monofunctional or polyfunctional isocyanates or epoxies, dehydrationcondensation reaction products with monofunctional or polyfunctionalcarboxylic acids, and the like are also preferably used. In addition,addition reactants between unsaturated carboxylic acid esters or amideshaving electrophilic substituents such as isocyanate groups and epoxygroups and monofunctional or polyfunctional alcohols, amines, or thiols,furthermore, substitution reaction products between unsaturatedcarboxylic acid esters or amides having dissociable substituents such ashalogen atoms and tosyloxy groups and monofunctional or polyfunctionalalcohols, amines, or thiols are also preferred. In addition, asadditional examples, compound groups obtained by substituting theunsaturated carboxylic acids with unsaturated phosphonic acids, styrene,vinyl ethers, or the like can also be used. These compounds aredescribed in JP2006-508380A, JP2002-287344A, JP2008-256850A,JP2001-342222A, JP1997-179296A (JP-H09-179296A), JP1997-179297A(JP-H09-179297A), JP1997-179298A (JP-H09-179298A), JP2004-294935A,JP2006-243493A, JP2002-275129A, JP2003-064130A, JP2003-280187A,JP1998-333321A (JP-H10-333321A), and the like.

As specific examples of monomers of esters of polyhydric alcoholcompounds and unsaturated carboxylic acids, examples of acrylic acidesters include ethylene glycol diacrylate, 1,3-butanediol diacrylate,tetramethylene glycol diacrylate, propylene glycol diacrylate,trimethylolpropane triacrylate, hexanediol diacrylate, tetraethyleneglycol diacrylate, pentaerythritol tetraacrylate, sorbitol triacrylate,isocyanuric acid ethylene oxide (EO)-modified triacrylate, polyesteracrylate oligomers, and the like. Examples of methacrylic acid estersinclude tetramethylene glycol dimethacrylate, neopentyl glycoldimethacrylate, trimethylolpropane trimethacrylate, ethylene glycoldimethacrylate, pentaerythritol trimethacrylate,bis[p-(3-methacryloxy-2-hydroxypropoxy)phenyl] dimethyl methane,bis[p-(methacryloxyethoxy)phenyl] dimethyl methane, and the like. Inaddition, specific examples of monomers of amides of polyvalent aminecompounds and unsaturated carboxylic acids include methylenebisacrylamide, methylene bismethacrylamide, 1,6-hexamethylenebisacrylamide, 1,6-hexamethylene bismethacrylamide, diethylenetriaminetrisacrylamide, xylene bisacrylamide, xylene bismethacrylamide, and thelike.

In addition, urethane-based addition polymerizable compounds producedusing an addition reaction between an isocyanate and a hydroxy group arealso preferred, and specific examples thereof include vinyl urethanecompounds having two or more polymerizable vinyl groups in one moleculeobtained by adding vinyl monomers having a hydroxy group represented byFormula (M) to a polyisocyanate compound having two or more isocyanategroups in one molecule which is described in, for example,JP1973-041708B (JP-S48-041708B).

CH₂═C(R^(M4))COOCH₂CH(R^(M5))OH  (M)

In Formula (M), R^(M4) and R^(M5) each independently represent ahydrogen atom or a methyl group.

In addition, urethane acrylates described in JP1976-037193A(JP-S51-037193A), JP1990-032293B (JP-H02-032293B), JP1990-016765B(JP-H02-016765B), JP2003-344997A, and JP2006-065210A, urethane compoundshaving ethylene oxide-based skeletons described in JP1983-049860B(JP-S58-049860B), JP1981-017654B (JP-S56-017654B), JP1987-039417B(JP-S62-039417B), JP 1987-039418B (JP-S62-039418B), JP2000-250211A, andJP2007-094138A, and urethane compounds having hydrophilic groupsdescribed in U.S. Pat. No. 7,153,632B, JP1996-505958A (JP-H08-505958A),JP2007-293221A, and JP2007-293223A are also preferred.

The content of the polymerizable compound is preferably in a range of 5%by mass to 75% by mass, more preferably in a range of 10% by mass to 70%by mass, and particularly preferably in a range of 15% by mass to 60% bymass of the total mass of the image-recording layer.

—Binder Polymer—

The image-recording layer that is used in the present disclosurepreferably contains a binder polymer. The binder polymer is preferably a(meth)acrylic resin, a polyvinyl acetal resin, or a polyurethane resin.In the present specification, “(meth)acrylic” indicates “acrylic” and“methacrylic”.

Among these, as the binder polymer, it is possible to preferably usewell-known binder polymers that can be used in the image-recording layerin the lithographic printing plate precursor. As an example, a binderpolymer that is used for an on-machine development-type lithographicprinting plate precursor (hereinafter, also referred to as the binderpolymer for on-machine development) will be described in detail.

As the binder polymer for on-machine development, a binder polymerhaving an alkylene oxide chain is preferred. The binder polymer havingan alkylene oxide chain may have a poly(alkylene oxide) portion in amain chain or in a side chain. In addition, the binder polymer may be agraft polymer having poly(alkylene oxide) in a side chain or a blockcopolymer of a block constituted of a poly(alkylene oxide)-containingrepeating unit and a block constituted of an (alkyleneoxide)-non-containing repeating unit.

In the case of having a poly(alkylene oxide) portion in the main chain,the binder polymer is preferably a polyurethane resin. As a polymer inthe main chain in a case in which the binder polymer has a poly(alkyleneoxide) portion in the side chain, a (meth)acrylic resin, a polyvinylacetal resin, a polyurethane resin, a polyurea resin, a polyimide resin,a polyamide resin, an epoxy resin, a polystyrene resin, a novolac-typephenol resin, a polyester resin, synthetic rubber, and natural rubberare exemplified, and, particularly, a (meth)acrylic resin is preferred.

The alkylene oxide is preferably alkylene oxide having 2 to 6 carbonatoms and particularly preferably ethylene oxide or propylene oxide.

The number of times of repetition of the alkylene oxide in thepoly(alkylene oxide) portion is preferably 2 to 120, more preferably 2to 70, and still more preferably 2 to 50.

In a case in which the number of times of repetition of the alkyleneoxide is 120 or less, neither the printing resistance against wear northe printing resistance against the ink-receiving property degrades,which is preferable.

The poly(alkylene oxide) portion is preferably contained in a form of astructure represented by Formula (AO) as the side chain of the binderpolymer and more preferably contained in a form of the structurerepresented by Formula (AO) as the side chain of the (meth)acrylicresin.

In Formula (AO), y represents 2 to 120, R₁ represents a hydrogen atom oran alkyl group, and R₂ represents a hydrogen atom or a monovalentorganic group.

The monovalent organic group is preferably an alkyl group having 1 to 6carbon atoms, and, a methyl group, an ethyl group, an n-propyl group, anisopropyl group, an n-butyl group, a sec-butyl group, an isobutyl group,a tert-butyl group, an n-pentyl group, an isopentyl group, a neopentylgroup, an n-hexyl group, an isohexyl group, a 1,1-dimethylbutyl group, a2,2-dimethylbutyl group, a cyclopentyl group, and a cyclohexyl group areexemplified.

In Formula (AO), y is preferably 2 to 70 and more preferably 2 to 50. R₁is preferably a hydrogen atom or a methyl group and particularlypreferably a hydrogen atom. R₂ is particularly preferably a hydrogenatom or a methyl group.

The binder polymer may have a crosslinking property in order to improvethe membrane hardness of an image area. In order to provide acrosslinking property to the polymer, a crosslinking functional groupsuch as an ethylenically unsaturated bond may be introduced to a mainchain or a side chain of a polymer. The crosslinking functional groupmay be introduced by copolymerization or may be introduced by a polymerreaction.

Examples of a polymer having an ethylenically unsaturated bond in themain chain of the molecule include poly-1,4-butadiene,poly-1,4-isoprene, and the like.

Examples of a polymer having an ethylenically unsaturated bond in theside chain of the molecule include polymers that are an ester or anamide of acrylic acid or methacrylic acid and in which a residue (R in—COOR or —CONHR) of the ester or the amide is a polymer having anethylenically unsaturated bond.

Examples of the residue (the R) having an ethylenically unsaturated bondcan include —(CH₂)_(n)CR^(1A)═CR^(2A)R^(3A),—(CH₂O)_(n)CH₂CR^(1A)═CR^(2A)R^(3A),—(CH₂CH₂O)_(n)CH₂CR^(1A)═CR^(2A)R^(3A),—(CH₂)_(n)NH—CO—CH₂CR^(1A)═CR^(2A)R^(3A),—(CH₂)_(n)—O—CO—CR^(1A)═CR^(2A)R^(3A), and —(CH₂CH₂O)₂—X (in theformulae, R^(A1) to R^(A3) each independently represent a hydrogen atom,a halogen atom, an alkyl group having 1 to 20 carbon atoms, an arylgroup, an alkoxy group, or an aryloxy group, and R^(A1) and R^(A2) orR^(A3) may be bonded to each other to form a ring. n represents aninteger of 1 to 10. X represents a dicyclopentadienyl residue.).

Specific examples of an ester residue include —CH₂CH═CH₂,—CH₂CH₂O—CH₂CH═CH₂, —CH₂C(CH₃)═CH₂, —CH₂CH═CH—C₆H₅,—CH₂CH₂OCOCH═CH—C₆H₅, —CH₂CH₂—NHCOO—CH₂CH═CH₂, and —CH₂CH₂O—X (in theformula, X represents a dicyclopentadienyl residue.).

Specific examples of an amide residue include —CH₂CH═CH₂, —CH₂CH₂—Y (inthe formula, Y represents a cyclohexene residue.), and—CH₂CH₂—OCO—CH═CH₂.

The binder polymer having a crosslinking property is cured as follows:for example, a free radical (a polymerization initiation radical or agrowth radical in a polymerization process of a polymerizable compound)is added to the crosslinking functional group, addition polymerizationoccurs between polymers directly or through the polymerization chain ofthe polymerizable compound, and a crosslink is formed between thepolymer molecules, whereby the polymer is cured. Alternatively, an atomin the polymer (for example, a hydrogen atom on a carbon atom adjacentto the crosslinking functional group) is pulled off by a free radical,polymer radicals are generated, and the polymer radicals are bonded toeach other, whereby a crosslink is formed between the polymer molecules,and the polymer is cured.

The content of the crosslinking group in the binder polymer (the contentof an unsaturated double bond that is radical polymerizable byiodimetry) is preferably 0.1 mmol to 10.0 mmol, more preferably 1.0 mmolto 7.0 mmol, and still more preferably 2.0 mmol to 5.5 mmol per gram ofthe binder polymer from the viewpoint of a favorable sensitivity and afavorable storage stability.

Hereinafter, specific examples 1 to 11 of the binder polymer foron-machine development will be illustrated, but the present disclosureis not limited thereto. In the following exemplary compounds, numericalvalues described together with individual repeating units (numericalvalues described together with main chain repeating units) represent themolar percentages of the above-described repeating units. Numericalvalues described together with side chain repeating units represent thenumber of times of repetition of the above-described repeating portions.In addition, Me represents a methyl group, Et represents an ethyl group,and Ph represents a phenyl group.

Regarding the molecular weight of the binder polymer, the weight-averagemolecular weight (Mw) as a polystyrene equivalent value by a GPC methodis preferably 2,000 or more, more preferably 5,000 or more, and stillmore preferably 10,000 to 300,000.

If necessary, it is possible to jointly use a hydrophilic polymer suchas polyacrylic acid or polyvinyl alcohol described in JP2008-195018A. Inaddition, it is also possible to jointly use a lipophilic polymer and ahydrophilic polymer.

The binder polymer may be present as a polymer that functions as abinder of the respective components or may be present in a particleshape in the image-recording layer. In a case in which the binderpolymer is present in a particle shape, the average primary particlediameter is preferably 10 nm to 1,000 nm, more preferably 20 nm to 300nm, and still more preferably 30 nm to 120 run.

Meanwhile, a compound corresponding to the polymer particle is regardednot to correspond to the binder polymer.

In the image-recording layer that is used in the present disclosure, thebinder polymer may be used singly or two or more binder polymers may bejointly used.

The binder polymer can be added to the image-recording layer in a randomamount. The content of the binder polymer can be appropriately selecteddepending on the application or the like of the image-recording layer,but is preferably 1% by mass to 90% by mass and more preferably 5% bymass to 80% by mass of the total mass of the image-recording layer.

—Radical Production Aid—

The image-recording layer that is used in the present disclosure maycontain a radical production aid. The radical production aid contributesto the improvement of the printing resistance of lithographic printingplates. Examples of the radical production aid include five kinds ofradical production aids described below.

(i) Alkyl or arylate complexes: It is considered that carbon-heterobonds are oxidatively cleaved and active radicals are generated.Specific examples thereof include borate compounds and the like.

(ii) Amino acetate compounds: It is considered that C—X bonds on carbonadjacent to nitrogen are cleaved due to oxidation and active radicalsare generated. X is preferably a hydrogen atom, a carboxy group, atrimethylsilyl group, or a benzyl group. Specific examples thereofinclude N-phenylglycines (which may have a substituent in a phenylgroup.), N-phenyl iminodiacetic acids (which may have a substituent in aphenyl group.), and the like.

(iii) Sulfur-containing compounds: The above-described amino acetatecompounds in which a nitrogen atom is substituted with a sulfur atom arecapable of generating active radicals by means of the same action.Specific examples thereof include phenylthioacetic acids (which may havea substituent in a phenyl group.) and the like.

(iv) Tin-containing compounds: The above-described amino acetatecompounds in which a nitrogen atom is substituted with a tin atom arecapable of generating active radicals by means of the same action.

(v) Sulfinates: Active radicals can be generated by means of oxidation.Specific examples thereof include sodium aryl sulfinate and the like.

Among these radical production aids, the image-recording layerpreferably contains a borate compound. The borate compound is preferablya tetraaryl borate compound or a monoalkyltriaryl borate compound, morepreferably a tetraaryl borate compound from the viewpoint of thestability of the compound and a potential difference described below,and particularly preferably a tetraaryl borate compound having one ormore aryl groups having an electron-attracting group from the viewpointof the potential difference described below.

The electron-attracting group is preferably a group having a positiveHammett σ value and more preferably a group having a Hammett σ value of0 to 1.2. Hammett σ values (a σp value and a urn value) are described indetail in Hansch, C.; Leo, A.; Taft, R. W., Chem. Rev., 1991, 91,165-195.

The electron-attracting group is preferably a halogen atom, atrifluoromethyl group, or a cyano group and more preferably a fluorineatom, a chlorine atom, a trifluoromethyl group, or a cyano group.

A counter cation in the borate compound is preferably an alkali metalion or a tetraalkyl ammonium ion and more preferably a sodium ion, apotassium ion, or a tetrabutylammonium ion.

Specific examples of the borate compound include compounds illustratedbelow. Here, X_(c) ⁺ represents a monovalent cation and is preferably analkali metal ion or a tetraalkyl ammonium ion and more preferably analkali metal ion or a tetrabutylammonium ion. In addition, Bu representsan n-butyl group.

Only one radical production aid may be added or two or more radicalproduction aids may be jointly used.

The content of the radical production aid is preferably 0.01% by mass to30% by mass, more preferably 0.05% by mass to 25% by mass, and stillmore preferably 0.1% by mass to 20% by mass of the total mass of theimage-recording layer.

—Chain Transfer Agent—

The image-recording layer that is used in the present disclosure maycontain a chain transfer agent. The chain transfer agent contributes tothe improvement of the printing resistance in lithographic printingplates.

The chain transfer agent is preferably a thiol compound, more preferablya thiol having 7 or more carbon atoms from the viewpoint of the boilingpoint (difficulty of being volatilized), and still more preferably acompound having a mercapto group on an aromatic ring (aromatic thiolcompound). The thiol compound is preferably a monofunctional thiolcompound.

Specific examples of the chain transfer agent include the followingcompounds.

Only one chain transfer agent may be added or two or more chain transferagents may be jointly used.

The content of the chain transfer agent is preferably 0.01% by mass to50% by mass, more preferably 0.05% by mass to 40% by mass, and stillmore preferably 0.1% by mass to 30% by mass of the total mass of theimage-recording layer.

—Additional Polymer Particle—

In order to improve the on-machine developability of the lithographicprinting plate precursor, the image-recording layer may contain anadditional polymer particle. The additional polymer particle ispreferably a polymer particle capable of converting the image-recordinglayer to be hydrophobic in the case of being irradiated with heat. Apolymer particle corresponding to the above-described polymer particleis regarded not to correspond to the other polymer particle. Theadditional polymer particle is preferably at least one selected from ahydrophobic thermoplastic polymer particle, a thermally reactive polymerparticle, a polymer particle having a polymerizable group, amicrocapsule including a hydrophobic compound, or a micro gel(crosslinking polymer particle). Among these, a polymer particle havinga polymerizable group and a micro gel are preferred.

As the hydrophobic thermoplastic polymer particle, hydrophobicthermoplastic polymer particles described in Research Disclosure No.33303 of January 1992 and the specifications of JP1997-123387A(JP-H09-123387A), JP1997-131850A (JP-H09-131850A), JP1997-171249A(JP-H09-171249A), JP1997-171250A (JP-H09-171250A), EP931647B, and thelike are preferably exemplified.

Specific examples of a polymer constituting the hydrophobicthermoplastic polymer particle include homopolymers or copolymers ofmonomers of ethylene, styrene, vinyl chloride, methyl acrylate, ethylacrylate, methyl methacrylate, ethyl methacrylate, vinylidene chloride,acrylonitrile, vinylcarbazole, acrylates or methacrylates havingpolyalkylene structures, and the like and mixtures thereof. Preferredexamples thereof include copolymers having polystyrene, styrene, andacrylonitrile and polymethyl methacrylate. The average particle diameterof the hydrophobic thermoplastic polymer particle is preferably in arange of 0.01 μm to 2.0 μm.

Examples of the thermally reactive polymer particle include a polymerparticle having a thermally reactive group. The polymer particle havinga thermally reactive group forms a hydrophobilized region throughcrosslinking by a thermal reaction and a change in a functional group atthis time.

The thermally reactive group in the polymer particle having a thermallyreactive group may be a functional group that causes any reactions aslong as chemical bonds are formed, but is preferably a polymerizablegroup. Preferred examples thereof include ethylenically unsaturatedgroups that cause radical polymerization reactions (for example,acryloyl groups, methacryloyl groups, vinyl groups, allyl groups, andthe like), cationic polymerizable groups (for example, vinyl groups,vinyloxy groups, epoxy groups, oxetanyl groups, and the like),isocyanato groups that cause addition reactions or blocked bodiesthereof, epoxy groups, vinyloxy groups, functional groups having activehydrogen atoms that are reaction partners thereof (for example, aminogroups, hydroxy groups, carboxy groups, and the like), carboxy groupsthat cause condensation reactions, hydroxy groups or amino groups thatare reaction partners, acid anhydrides that cause ring-opening additionreactions, amino groups or hydroxy groups which are reaction partners,and the like.

Examples of the microcapsules include microcapsules including all orpart of the constituent components of the image-recording layer asdescribed in JP2001-277740A and JP2001-277742A. The constituentcomponents of the image-recording layer can also be added outside themicrocapsules. A preferred aspect of the image-recording layer includingthe microcapsules is an image-recording layer including hydrophobicconstituent components in the microcapsules and including hydrophilicconstituent components outside the microcapsules.

Micro gels (crosslinking polymer particles) are capable of containingsome of the constituent components of the image-recording layer at leastone of in the inside or on the surface thereof. Particularly, an aspectof micro capsules that have radical polymerizable groups on the surfacesand thus turn into reactive micro gels is preferred from the viewpointof image-forming sensitivity or printing resistance.

In order to put the constituent components of the image-recording layerinto microcapsules or micro gels, well-known methods can be used.

The average particle diameter of the microcapsules or the micro gels ispreferably in a range of 0.01 μm to 3.0 μm, more preferably in a rangeof 0.05 μm to 2.0 μm, and particularly preferably in a range of 0.10 μmto 1.0 μM. Within this range, favorable resolution and temporalstability can be obtained.

The content of the polymer particle is preferably 5% by mass to 90% bymass of the total mass of the image-recording layer.

—Low-Molecular-Weight Hydrophilic Compound—

In order to improve the on-machine developability while suppressing thedegradation of printing resistance, the image-recording layer maycontain a low-molecular-weight hydrophilic compound. Thelow-molecular-weight hydrophilic compound is preferably a compoundhaving a molecular weight of smaller than 1,000, more preferably acompound having a molecular weight of smaller than 800, and still morepreferably a compound having a molecular weight of smaller than 500.

As the low-molecular-weight hydrophilic compound, examples ofwater-soluble organic compounds include glycols such as ethylene glycol,diethylene glycol, triethylene glycol, propylene glycol, dipropyleneglycol, and tripropylene glycol and ethers or ester derivative thereof,polyols such as glycerin, pentaerythritol, and tris(2-hydroxyethyl)isocyanurate, organic amines such as triethanolamine, diethanolamine,and monoethanolamine and salts thereof, organic sulfonic acids such asalkyl sulfonic acid, toluenesulfonic acid, and benzenesulfonic acid andsalts thereof, organic sulfamic acids such as alkyl sulfamate and saltsthereof, organic sulfuric acids such as alkyl sulfates and alkyl ethersulfates and salts thereof, organic phosphonic acids such asphenylphosphonic acid and salts thereof, organic carboxylic acids suchas tartaric acid, oxalic acid, citric acid, malic acid, lactic acid,gluconic acid, and amino acid and salts thereof, betaines, and the like.

As the low-molecular-weight hydrophilic compound, at least one selectedfrom polyols, organic sulfates, organic sulfonates, or betaines ispreferably contained.

Specific examples of the organic sulfonates include alkyl sulfonatessuch as sodium n-butyl sulfonate, sodium n-hexyl sulfonate, sodium2-ethylhexyl sulfonate, sodium cyclohexyl sulfonate, and sodium n-octylsulfonate; alkyl sulfonates having ethylene oxide chains such as sodium5,8,11-trioxapentadecane-1-sulfonate, sodium5,8,11-trioxaheptadecane-1-sulfonate, sodium13-ethyl-5,8,11-trioxaheptadecane-1-sulfonate, sodium5,8,11,14-tetraoxatetracosane-1-sulfonate; aryl sulfonates such assodium benzene sulfonate, sodium p-toluenesulfonate, sodiump-hydroxybenzene sulfonate, sodium p-styrene sulfonate, sodium dimethylisophthalate-5-sulfonate, sodium 1-naphthyl sulfonate, sodium4-hydroxynaphthylsulfonate, sodium 1,5-naphthalene disulfonate, andtrisodium 1,3,6-naphthalene trisulfonate; compounds described inParagraphs 0026 to 0031 of JP2007-276454A and Paragraphs 0020 to 0047 ofJP2009-154525A; and the like. The salts may be potassium salts orlithium salts.

Examples of the organic sulfates include sulfates of alkyls, alkenyls,alkynyls, aryls, or heterocyclic monoethers of polyethylene oxides. Thenumber of ethylene oxide units is preferably in a range of 1 to 4, andthe salts are preferably sodium salts, potassium salts, or lithiumsalts. Specific examples thereof include compounds described inParagraphs 0034 to 0038 of JP2007-276454A.

The betaines are preferably compounds in which the number of carbonatoms in hydrocarbon substituents into nitrogen atoms is in a range of 1to 5, and specific examples thereof include trimethyl ammonium acetate,dimethyl propyl ammonium acetate, 3-hydroxy-4-trimethyl ammoniobutyrate, 4-(1-pyridinio) butyrate, 1-hydroxyethyl-1-imidazolio acetate,trimethyl ammonium methanesulfonate, dimethyl propyl ammoniummethanesulfonate, 3-trimethylammonio-1-propane sulfonate,3-(1-pyridinio)-1-propane sulfonate, and the like.

Since the low-molecular-weight hydrophilic compound has a smallstructure in hydrophobic portions and barely has surfactant actions,there are no cases in which dampening water permeates exposed portions(image areas) in the image-recording layer and thus the hydrophobicproperties or membrane hardness of the image areas degrade, and it ispossible to favorably maintain the ink-receiving properties and printingresistance of the image-recording layer.

The content of the low-molecular-weight hydrophilic compound ispreferably in a range of 0.5% by mass to 20% by mass, more preferably ina range of 1% by mass to 15% by mass, and still more preferably in arange of 2% by mass to 10% by mass of the total mass of theimage-recording layer. In a case in which the content is in this range,favorable on-machine developability and favorable printing resistancecan be obtained.

The low-molecular-weight hydrophilic compound may be used singly or twoor more low-molecular-weight hydrophilic compounds may be used in amixture form.

—Sensitization Agent—

In order to improve the ink-absorbing property, the image-recordinglayer may contain a sensitization agent such as a phosphonium compound,a nitrogen-containing low-molecular-weight compound, or an ammoniumgroup-containing polymer. Particularly, in a case in which an inorganiclamellar compound is contained in the protective layer, these compoundsfunction as surface coating agents for the inorganic lamellar compoundand are capable of suppressing the ink-absorbing properties from beingdegraded in the middle of printing due to the inorganic lamellarcompound.

Among these, a phosphonium compound, a nitrogen-containinglow-molecular-weight compound, and an ammonium group-containing polymerare preferably jointly used as the sensitization agent, and aphosphonium compound, quaternary ammonium salts, and an ammoniumgroup-containing polymer are more preferably jointly used.

Examples of a phosphonium compound include phosphonium compoundsdescribed in JP2006-297907A and JP2007-050660A. Specific examplesthereof include tetrabutylphosphonium iodide, butyltriphenylphosphoniumbromide, tetraphenylphosphonium bromide,1,4-bis(triphenylphosphonio)butane=di(hexafluorophosphate),1,7-bis(triphenylphosphonio)heptane=sulfate,1,9-bis(triphenylphosphonio)nonane=naphthalene-2,7-disulfonate, and thelike.

Examples of the nitrogen-containing low-molecular-weight compoundinclude amine salts and quaternary ammonium salts. In addition, examplesthereof include imidazolinium salts, benzo imidazolinium salts,pyridinium salts, and quinolinium salts. Among these, quaternaryammonium salts and pyridinium salts are preferred. Specific examplesthereof include tetramethylammonium=hexafluorophosphate,tetrabutylammonium=hexafluorophosphate,dodecyltrimethylammonium=p-toluene sulfonate,benzyltriethylammonium=hexafluorophosphate,benzyldimethyloctylammonium=hexafluorophosphate,benzyldimethyldodecylammonium=hexafluorophosphate, compounds describedin Paragraphs 0021 to 0037 of JP2008-284858A and Paragraphs 0030 to 0057of JP2009-090645A, and the like.

The ammonium group-containing polymer needs to have an ammonium group inthe structure, and polymers including 5% by mol to 80% by mol of(meth)acrylate having ammonium groups in side chains as copolymerizationcomponents are preferred. Specific examples thereof include polymersdescribed in Paragraphs 0089 to 0105 of JP2009-208458A.

In the ammonium group-containing polymer, the value of the reducingspecific viscosity (unit: ml/g) obtained according to the measurementmethod described in JP2009-208458A is preferably in a range of 5 to 120,more preferably in a range of 10 to 110, and particularly preferably ina range of 15 to 100. In a case in which the reducing specific viscosityis converted to the weight-average molecular weight (Mw), theweight-average molecular weight is preferably in a range of 10,000 to150,000, more preferably in a range of 17,000 to 140,000, andparticularly preferably in a range of 20,000 to 130,000.

Hereinafter, specific examples of the ammonium group-containing polymerwill be described.

(1) 2-(Trimethylammonio)ethylmethacrylate=p-toluenesulfonate/3,6-dioxaheptyl methacrylate copolymer(molar ratio: 10/90, Mw: 45,000)

(2) 2-(Trimethylammonio)ethylmethacrylate=hexafluorophosphate/3,6-dioxaheptyl methacrylate copolymer(molar ratio: 20/80, Mw: 60,000)

(3) 2-(Ethyldimethylammonio)ethyl methacrylate=p-toluenesulfonate/hexylmethacrylate copolymer (molar ratio: 30/70, Mw: 45,000)

(4) 2-(Trimethylammonio)ethylmethacrylate=hexafluorophosphate/2-ethylhexyl methacrylate copolymer(molar ratio: 20/80, Mw: 60,000)

(5) 2-(Trimethylammonio)ethyl methacrylate=methylsulfate/hexylmethacrylate copolymer (molar ratio: 40/60, Mw: 70,000)

(6) 2-(Butyldimethylammonio)ethylmethacrylate=hexafluorophosphate/3,6-dioxaheptyl methacrylate copolymer(molar ratio: 25/75, Mw: 65,000)

(7) 2-(Butyldimethylammonio)ethylacrylate=haxafluorophosphate/3,6-dioxaheptyl methacrylate copolymer(molar ratio: 20/80, Mw: 65,000)

(8) 2-(Butyldimethylammonio)ethylmethacrylate=13-ethyl-5,8,11-trioxa-1-heptadecanesulfonate/3,6-dioxaheptylmethacrylate copolymer (molar ratio: 20/80, Mw: 75,000)

(9) 2-(Butyldimethylammonio) ethylmethacrylate=haxafluorophosphate/3,6-dioxaheptylmethacrylate/2-hydroxy-3-methacryloyloxypropyl methacrylate copolymer(molar ratio: 15/80/5, Mw: 65,000)

The content of the sensitization agent is preferably in a range of 0.01%by mass to 30.0% by mass, more preferably in a range of 0.1% by mass to15.0% by mass, and still more preferably in a range of 1% by mass to 10%by mass of the total mass of the image-recording layer.

—Acid Color Developing Agent—

The image-recording layer that is used in the present disclosurepreferably includes an acid color developing agent.

The “acid color developing agent” that is used in the present disclosurerefers to a compound having a property of developing color by beingheated in a state of receiving an electron-receiving compound (forexample, a proton such as an acid). The acid color developing agent isparticularly preferably a colorless compound which has a partialskeleton such as lactone, lactam, sultone, spiropyran, an ester, or anamide and in which the partial skeleton rapidly ring-opens or cleavagesin the case of coming into contact with the electron-receiving compound.

Examples of the above-described acid color developing agent includephthalides such as3,3-bis(4-dimethylaminophenyl)-6-dimethylaminophthalide (referred to as“crystal violet lactone”), 3,3-bis(4-dimethylaminophenyl)phthalide,3-(4-dimethylaminophenyl)-3-(4-diethylamino-2-methylphenyl)-6-dimethylaminophthalide,3-(4-dimethylaminophenyl)-3-(1,2-dimethylindol-3-yl)phthalide,3-(4-dimethylaminophenyl)-3-(2-methyl indol-3-yl)phthalide,3,3-bis(1,2-dimethylindol-3-yl)-5-dimethylaminophthalide,3,3-bis(1,2-dimethylindol-3-yl)-6-dimethylaminophthalide,3,3-bis(9-ethylcarbazole-3-yl)-6-dimethylaminophthalide,3,3-bis(2-phenylindol-3-yl)-6-dimethylaminophthalide,3-(4-dimethylaminophenyl)-3-(1-methylpyrrole-3-yl)-6-dimethylaminophthalide,

3,3-bis[1,1-bis(4-dimethylaminophenyl)ethylene-2-yl]-4,5,6,7-tetrachlorophthalide,3,3-bis[1,1-bis(4-pyrrolidinophenyl)ethylene-2-yl]-4,5,6,7-tetrabromophthalide,3,3-bis[1-(4-dimethylaminophenyl)-1-(4-methoxyphenyl)ethylene-2-yl]-4,5,6,7-tetrachlorophthalide,3,3-bis[1-(4-pyrrolidinophenyl)-1-(4-methoxyphenyl)ethylene-2-yl]-4,5,6,7-tetrachlorophthalide,3-[1,1-di(1-ethyl-2-methylindol-3-yl)ethylene-2-yl]-3-(4-diethylaminophenyl)phthalide,3-[1,1-di(1-ethyl-2-methylindol-3-yl)ethylene-2-yl]-3-(4-N-ethyl-N-phenylaminophenyl)phthalide,3-(2-ethoxy-4-diethylaminophenyl)-3-(1-n-octyl-2-methylindol-3-yl)-phthalide,3,3-bis(1-n-octyl-2-methylindol-3-yl)-phthalide, and3-(2-methyl-4-diethylaminophenyl)-3-(1-n-octyl-2-methylindol-3-yl)-phthalide,

fluoranthenes such as 4,4-bis-dimethylaminobenzhydryl benzyl ether,N-halophenyl-leucoauramine, N-2,4,5-trichlorophenyl leucoauramine,rhodamine-B-anilinolactam, rhodamine-(4-nitroanilino) lactam,rhodamine-B-(4-chloroanilino) lactam,3,7-bis(diethylamino)-10-benzoylphenoxazine, benzoyl leuco methyleneblue, 4-nitrobenzoylmethylene blue,

3,6-dimethoxyfluoran, 3-dimethylamino-7-methoxyfluoran,3-diethylamino-6-methoxyfluoran, 3-diethylamino-7-methoxyfluoran,3-diethylamino-7-chlorofluoran, 3-diethylamino-6-methyl-7-chlorofluoran,3-diethylamino-6,7-dimethylfluoran,3-N-cyclohexyl-N-n-butylamino-7-methylfluoran,3-diethylamino-7-dibenzylaminofluoran,3-diethylamino-7-octylaminofluoran,3-diethylamino-7-di-n-hexylaminofluoran,3-diethylamino-7-anilinofluoran,3-diethylamino-7-(2′-fluorophenylamino)fluoran,3-diethylamino-7-(2′-chlorophenylamino)fluoran,3-diethylamino-7-(3′-chlorophenylamino)fluoran,3-diethylamino-7-(2′,3′-dichlorophenylamino)fluoran,3-diethylamino-7-(3′-trifluoromethylphenylamino)fluorane,3-di-n-butylamino-7-(2′-fluorophenylamino)fluoran,3-di-n-butylamino-7-(2′-chlorophenylamino)fluoran,3-N-isopentyl-N-ethylamino-7-(2′-chlorophenylamino)fluorane,

3-N-n-hexyl-N-ethylamino-7-(T-chlorophenylamino)fluoran,3-diethylamino-6-chloro-7-anilinofluoran,3-di-n-butylamino-6-chloro-7-anilinofluoran,3-diethylamino-6-methoxy-7-anilinofluoran,3-di-n-butylamino-6-ethoxy-7-anilinofluoran,3-pyrrolidino-6-methyl-7-anilinofluoran,3-piperidino-6-methyl-7-anilinofluoran,3-morpholino-6-methyl-7-anilinofluoran,3-dimethylamino-6-methyl-7-anilinofluoran,3-diethylamino-6-methyl-7-anilinofluoran,3-di-n-butylamino-6-methyl-7-anilinofluoran,3-di-n-pentylamino-6-methyl-7-anilinofluoran,3-N-ethyl-N-methylamino-6-methyl-7-anilinofluoran,3-N-n-propyl-N-methylamino-6-methyl-7-anilinofluoran,3-N-n-propyl-N-ethylamino-6-methyl-7-anilinofluoran,3-N-n-butyl-N-methylamino-6-methyl-7-anilinofluoran,3-N-n-butyl-N-ethylamino-6-methyl-7-anilinofluoran,3-N-isobutyl-N-ethylamino-6-methyl-7-anilinofluoran,3-N-isobutyl-N-ethylamino-6-methyl-7-anilinofluoran,3-N-isopentyl-N-ethylamino-6-methyl-7-anilinofluoran,3-N-n-hexyl-N-methylamino-6-methyl-7-anilinofluoran,3-N-cyclohexyl-N-ethylamino-6-methyl-7-anilinofluoran,3-N-cyclohexyl-N-n-propylamino-6-methyl-7-anilinofluoran,3-N-cyclohexyl-N-n-butylamino-6-methyl-7-anilinofluoran,3-N-cyclohexyl-N-n-hexyl amino-6-methyl-7-anilinofluoran,3-N-cyclohexyl-N-n-octylamino-6-methyl-7-anilinofluoran,

3-N-(2′-methoxyethyl)-N-methylamino-6-methyl-7-anilinofluoran,3-N-(2′-methoxyethyl)-N-ethylamino-6-methyl-7-anilinofluoran,3-N-(2′-methoxyethyl)-N-isobutylamino-6-methyl-7-anilinofluoran,3-N-(2′-ethoxyethyl)-N-methylamino-6-methyl-7-anilinofluoran,3-N-(2′-ethoxyethyl)-N-ethylamino-6-methyl-7-anilinofluoran,3-N-(3′-methoxypropyl)-N-methylamino-6-methyl-7-anilinofluoran,3-N-(3′-methoxypropyl)-N-ethylamino-6-methyl-7-anilinofluoran,3-N-(3′-ethoxypropyl)-N-ethylamino-6-methyl-7-anilinofluoran,3-N-(3′-ethoxypropyl)-N-methylamino-6-methyl-7-anilinofluoran,3-N-(2′-tetrahydrofurfuryl)-N-ethylamino-6-methyl-7-anilinofluoran,3-N-(4′-methylphenyl)-N-ethylamino-6-methyl-7-anilinofluoran,3-diethylamino-6-ethyl-7-anilinofluran,3-diethylamino-6-methyl-7-(3′-methylphenylamino)fluoran,3-diethylamino-6-methyl-7-(2′,6′-methylphenylamino)fluoran,3-di-n-butylamino-6-methyl-7-(2′,6′-methylphenylamino)fluoran,3-di-n-butylamino-7-(2′,6′-dimethylphenylamino)fluoran,2,2-bis[4′-(3-N-cyclohexyl-N-methylamino-6-methylfluoran)-7-ylaminophenyl]propane,3-[4′-(4-phenylaminophenyl)aminophenyl]amino-6-methyl-7-chlorofluoran,and 3-[4′-(dimethylaminophenyl)]amino-5,7-dimethylfluoran,

phthalides such as3-(2-methyl-4-diethylaminophenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide,3-(2-n-propoxycarbonylamino-4-di-n-propylaminophenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide,3-(2-methylamino-4-di-n-propylaminophenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide,3-(2-methyl-4-di-n-hexylaminophenyl)-3-(1-n-octyl-2-methylindol-3-yl)-4,7-diazaphthalide,3,3-bis(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3,3-bis(1-n-octyl-2-methylindol-3-yl)-4-azaphthalide,3-(2-ethoxy-4-diethylaminophenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide,3-(2-ethoxy-4-diethylaminophenyl)-3-(1-octyl-2-methylindol-3-yl)-4 or7-azaphthalide,3-(2-ethoxy-4-diethylaminophenyl)-3-(1-ethyl-2-methylindol-3-yl)-4 or7-azaphthalide,3-(2-hexyloxy-4-diethylaminophenyl)-3-(1-ethyl-2-methylindol-3-yl)-4 or7-azaphthalide,3-(2-ethoxy-4-diethylaminophenyl)-3-(1-ethyl-2-phenylindol-3-yl)-4 or7-azaphthalide,3-(2-butoxy-4-diethylaminophenyl)-3-(1-ethyl-2-phenylindol-3-yl)-4 or7-azaphthalide, 3-methyl-spiro-dinaphthopyran,3-ethyl-spiro-dinaphthopyran, 3-phenyl-spiro-dinaphthopyran,3-benzyl-spiro-dinaphthopyran,3-methyl-naphtho-(3-methoxybenzo)spiropyran,3-propyl-spiro-dibenzopyran-3,6-bis(dimethylamino)fluorene-9-spiro-3′-(6′-dimethylamino)phthalide,and3,6-bis(diethylamino)fluorene-9-spiro-3′-(6′-dimethylamino)phthalide,

additionally,2′-anilino-6′-(N-ethyl-N-isopentyl)amino-3′-methylspiro[isobenzofuran-(3H),9′-(9H) xanthene]-3-one,2′-anilino-6′-(N-ethyl-N-(4-methylphenyl))amino-3′-methylspiro[isobenzofuran-1(3H), 9′-(9H) xanthene]-3-one, 3′-N,N-dibenzylamino-6′-N,N-diethylaminospiro[isobenzofuran-1 (3H), 9′-(9H)xanthene]-3-one,2′-(N-methyl-N-phenyl)amino-6′-(N-ethyl-N-(4-methylphenyl))aminospiro[isobenzofuran-1 (3H), 9′-(9H) xanthene]-3-one, and the like.

Among these, the acid color developing agent that is used in the presentdisclosure is preferably at least one compound selected from the groupconsisting of a spiropyran compound, a spirooxazine compound, aspirolactone compound, or a spirolactam compound.

The hue of the colorant after color development is preferably green,blue, or black from the viewpoint of visibility.

As the acid color developing agent, it is also possible to usecommercially available products, and examples thereof include ETAC, RED500, RED 520, CVL, S-205, BLACK 305, BLACK 400, BLACK 100, BLACK 500,H-7001, GREEN 300, NIRBLACK 78, BLUE 220, H-3035, BLUE 203, ATP, H-1046,H-2114 (all manufactured by Fukui Yamada Chemical Co., Ltd.),ORANGE-DCF, Vemiilion-DCF, PINK-DCF, RED-DCF, BLMB, CVL, GREEN-DCF,TH-107 (all manufactured by Hodogaya Chemical Co., Ltd.), ODB, ODB-2,ODB-4, ODB-250, ODB-Black XV, Blue-63, Blue-502, GN-169, GN-2,Green-118, Red-40, Red-8 (all manufactured by Yamamoto Chemicals Inc.),crystal violet lactone (manufactured by Tokyo Chemical Industry Co.,Ltd.), and the like. Among these commercially available products, ETAC,S-205, BLACK 305, BLACK 400, BLACK 100, BLACK 500, H-7001, GREEN 300,NIRBLACK 78, H-3035, ATP, H-1046, H-2114, GREEN-DCF, Blue-63, GN-169,and crystal violet lactone are preferred since the visible lightabsorbance of films to be formed is favorable.

These acid color developing agents may be used singly, or two or morecomponents can also be used in combination.

—Coloring Agent—

The image-recording layer in the lithographic printing plate precursorof the embodiment of the present disclosure may contain a dye having ahigh absorption in the visible light range as a coloring agent ofimages. Specific examples thereof include OIL YELLOW #101, OIL YELLOW#103, OIL PINK #312, OIL GREEN BG, OIL BLUE BOS, OIL BLUE #603, OILBLACK BY, OIL BLACK BS, OIL BLACK T-505 (all manufactured by OrientChemical Industries, Ltd.), VICTORIA PURE BLUE, CRYSTAL VIOLET(CI42555), METHYL VIOLET (CI42535), ETHYL VIOLET, ETHYL VIOLET 6HNAPS,RHODAMINE B (CI145170B), MALACHITE GREEN (CI42000), METHYLENE BLUE(CI52015), and dyes described in JP1987-293247A (JP-S62-293247A). Inaddition, pigments such as phthalocyanine-based pigment, azo-basedpigments, carbon black, and titanium oxide can also be preferably used.The image-recording layer preferably contains a coloring agent since itbecomes easy to differentiate an image area and a non-image area afterthe formation of an image in the case of containing the coloring agent.

The amount of the coloring agent added is preferably 0.005% by mass to10% by mass of the total mass of the image-recording layer.

—Other Components—

To the image-recording layer, it is possible to add, as othercomponents, a surfactant, a polymerization inhibitor, a higher-fattyacid derivative, a plasticizer, inorganic particles, an inorganiclamellar compound, or the like. Specifically, the composition maycontain individual components described in Paragraphs 0114 to 0159 ofJP2008-284817A.

—Formation of Image-Recording Layer—

The image-recording layer in the lithographic printing plate precursoraccording to the embodiment of the present disclosure can be formed by,for example, as described in Paragraphs 0142 and 0143 of JP2008-195018A,preparing a coating fluid by dispersing or dissolving the respectivenecessary components described above in a well-known solvent, applyingthe coating fluid onto a support using a well-known method such as barcoater coating, and drying the coating fluid. The coating amount (solidcontent) of the image-recording layer applied after application anddrying varies depending on applications; however, is preferably 0.3 g/m²to 3.0 g/m². Within this range, a favorable sensitivity and favorablemembrane characteristics of the image-recording layer can be obtained.

<Hydrophilic Support>

The hydrophilic support in the lithographic printing plate precursoraccording to the embodiment of the present disclosure (hereinafter, alsosimply referred to as “support”.) can be appropriately selected fromwell-known hydrophilic supports for a lithographic printing plateprecursor and used. The hydrophilic support is preferably an aluminumplate which has been roughened using a well-known method and anodized.

On the aluminum plate, as necessary, enlargement processes or sealingprocesses of micropores in anodized films described in JP2001-253181Aand JP2001-322365A, surface hydrophilization processes using alkalimetal silicate as described in the specifications of US2,714,066A,US3,181,461A, US3,280,734A, and US3,902,734A, and surfacehydrophilization processes using polyvinyl phosphate or the like asdescribed in the specifications of US3,276,868A, US4,153,461A, andUS4,689,272A may be appropriately selected and carried out.

In the support, the center line average roughness is preferably in arange of 0.10 μm to 1.2 μm.

The support may have, as necessary, a backcoat layer including anorganic polymer compound described in JP1993-045885A (JP-H05-045885A) oran alkoxy compound of silicon described in JP1994-035174A(JP-H06-035174A) on the surface opposite to the image-recording layer.

<Undercoat Layer>

The lithographic printing plate precursor according to the embodiment ofthe disclosure preferably has an undercoat layer (in some cases,referred to as the interlayer) between the image-recording layer and thesupport. The undercoat layer strengthens adhesiveness between thesupport and the image-recording layer in exposed portions andfacilitates peeling the support and the image-recording layer innon-exposed portions, and thus the undercoat layer contributes toimproving developability without impairing printing resistance. Inaddition, in the case of exposure using infrared lasers, the undercoatlayer functions as an adiabatic layer and thus has an effect ofpreventing the sensitivity from being degraded due to the diffusion ofheat generated by exposure in the support.

Examples of compounds that can be used for the undercoat layer includepolymers having adsorbent groups that can be adsorbed to the surface ofthe support and hydrophilic groups. In order to improve adhesiveness tothe image-recording layer, polymers having adsorbent groups andhydrophilic groups and further having crosslinking groups are preferred.The compounds that can be used for the undercoat layer may below-molecular-weight compounds or polymers. The compounds that can beused for the undercoat layer may be used in a mixed form of two or morekinds as necessary.

In a case in which the compounds that are used for the undercoat layerare polymers, copolymers of monomers having adsorbent groups, monomershaving hydrophilic groups, and monomers having crosslinking groups arepreferred.

The adsorbent groups that can be adsorbed to the surface of the supportare preferably phenolic hydroxy groups, carboxy groups, —PO₃H₂, —OPO₃H₂,—CONHSO₂—, —SO₂NHSO₂—, —COCH₂COCH₃. The hydrophilic groups arepreferably sulfo groups or salts thereof and salts of carboxy groups.The crosslinking groups are preferably acrylic groups, methacryl groups,acrylamide groups, methacrylamide groups, allyl groups, and the like.

The polymers may have crosslinking groups introduced due to theformation of salts between polar substituents of the polymers andcompounds having substituents having the polar substituents and oppositecharges of the above-described polar substituents and ethylenicallyunsaturated bonds and may be further copolymerized with monomers otherthan the above-described monomers, preferably, hydrophilic monomers.

Specifically, preferred examples thereof include silane coupling agentshaving ethylenic double bond reactive groups that are capable ofaddition polymerization described in JP1998-282679A (JP-H10-282679A) andphosphorus compounds having ethylenic double bond reactive groupsdescribed in JP1990-304441A (JP-H02-304441A). Low-molecular-weight orhigh-molecular-weight compounds having crosslinking groups (preferablyethylenically unsaturated bond groups), functional groups that interactwith the surface of the support, and hydrophilic groups described inJP2005-238816A, JP2005-125749A, JP2006-239867A, and JP2006-215263A arealso preferably used.

More preferred examples thereof include high-molecular-weight polymershaving adsorbent groups that can be adsorbed to the surface of thesupport, hydrophilic groups, and crosslinking groups described inJP2005-125749A and JP2006-188038A.

The content of ethylenically unsaturated bond groups in the polymer thatis used in the undercoat layer is preferably in a range of 0.1 mmol to10.0 mmol and more preferably in a range of 0.2 mmol to 5.5 mmol pergram of the polymer.

The weight-average molecular weight (Mw) of the polymer that is used inthe undercoat layer is preferably 5,000 or higher and more preferably ina range of 10,000 to 300,000.

In addition to the above-described compounds for the undercoat layer,the undercoat layer may also include a chelating agent, secondary ortertiary amines, a polymerization inhibitor, compounds having aminogroups or functional groups having a polymerization-inhibiting functionand groups that interact with the surfaces of supports (for example,1,4-diazabicyclo[2.2.2]octane (DABCO), 2,3,5,6-tetrahydroxy-p-quinone,chloranil, sulfophthalic acid, hydroxyethyl ethylene diamine triaceticacid, dihydroxyethyl ethylenediamine diacetic acid, hydroxyethyliminodiacetic acid, and the like), and the like in order to preventcontamination over time.

The undercoat layer is formed using well-known coating methods. Thecoating amount (solid content) of the undercoat layer is preferably in arange of 0.1 mg/m² to 100 mg/m² and more preferably in a range of 1mg/m² to 30 mg/m².

<Protective Layer>

The lithographic printing plate precursor according to the embodiment ofthe disclosure preferably has a protective layer (in some cases, alsoreferred to as the overcoat layer) on the image-recording layer. Theprotective layer has a function of suppressing imageformation-inhibiting reactions caused by the shielding of oxygen andadditionally has a function of preventing the generation of damage inthe image-recording layer and abrasion prevention during exposure usinghigh-illuminance lasers.

Protective layers having the above-described characteristics aredescribed in, for example, the specification of U.S. Pat. No. 3,458,311Aand JP1980-049729B (JP-S55-049729B). As poor oxygen-transmissiblepolymers that can be used for the protective layer, it is possible toappropriately select and use any one of water-soluble polymers andwater-insoluble polymers, and, if necessary, it is also possible to usetwo or more polymers in a mixed form. Specific examples thereof includepolyvinyl alcohols, modified polyvinyl alcohols, polyvinyl pyrrolidone,water-soluble cellulose derivatives, poly(meth)acrylonitrile, and thelike.

As the modified polyvinyl alcohols, acid-modified polyvinyl alcoholshaving carboxy groups or sulfo groups are preferably used. Specificexamples thereof include modified-polyvinyl alcohols described inJP2005-250216A and JP2006-259137A.

The protective layer preferably includes inorganic lamellar compounds inorder to enhance oxygen-shielding properties. The inorganic lamellarcompounds refer to particles having thin flat plate shapes, and examplesthereof include mica groups such as natural mica and synthetic mica,talc represented by Formula 3MgO.4SiO.H₂O, taeniolite, montmorillonite,saponite, hectorite, zirconium phosphate, and the like.

The inorganic lamellar compounds that can be preferably used are micacompounds. Examples of mica compounds include mica groups such asnatural mica and synthetic mica represented by Formula: A(B,C)₂₋₅D₄O₁₀(OH, F, O)₂ [here, A is any of K, Na, or Ca, B and C are anyof Fe (II), Fe (III), Mn, Al, Mg, and V, and D is Si or Al.].

In the mica groups, examples of natural mica include white mica, sodamica, gold mica, black mica, and lepidolite. Examples of synthetic micainclude non-swelling mica such as fluorphlogopite KMg₃(AlSi₃O₁₀)F₂,potassium tetrasilic mica KMg_(2.5)(Si₄O₁₀)F₂, and, Na tetrasilylic micaNaMg_(2.5)(Si₄O₁₀)F₂, swelling mica such as Na or Li taeniolite (Na,Li)Mg₂Li(Si₄O₁₀)F₂, montmorillonite-based Na or Li hectorite (Na,Li)_(1/8)Mg_(2/5)Li_(1/8)(Si₄O₁₀)F₂, and the like. Furthermore,synthetic smectite is also useful.

Among the above-described mica compounds, fluorine-based swelling micais particularly useful. That is, swelling synthetic mica has a laminatestructure consisting of unit crystal lattice layers having a thicknessin a range of approximately 10A to 15A (1A is equal to 0.1 run), andmetal atoms in lattices are more actively substituted than in any otherclay minerals. As a result, positive charges are deficient in thelattice layers, and positive ions such as Li⁺, Na⁺, Ca²⁺, and Mg²⁺ areadsorbed between the layers in order to compensate for the deficiency.Positive ions interposed between the layers are referred to asexchangeable positive ions and are exchangeable with various positiveions. Particularly, in a case in which the positive ions between thelayers are Li⁺ and Na⁺, the ionic radii are small, and thus the bondsbetween lamellar crystal lattices are weak, and mica is significantlyswollen by water. In a case in which shear is applied in this state,mica easily cleavages and forms a stable sol in water. Theabove-described tendency of swelling synthetic mica is strong, and theswelling synthetic mica is particularly preferably used.

From the viewpoint of diffusion control, regarding the shapes of themica compounds, the thickness is preferably thin, and the planar size ispreferably large as long as the smoothness and active lightray-transmitting properties of coated surfaces are not impaired.Therefore, the aspect ratio is preferably 20 or higher, more preferably100 or higher, and particularly preferably 200 or higher. The aspectratio is the ratio of the long diameter to the thickness of a particleand can be measured from projection views obtained from themicrophotograph of the particle. As the aspect ratio increases, theobtained effect becomes stronger.

Regarding the particle diameters of the mica compound, the average longdiameter thereof is preferably in a range of 0.3 μm to 20 μm, morepreferably in a range of 0.5 μm to 10 μm, and particularly preferably ina range of 1 μm to 5 μm. The average thickness of the particles ispreferably 0.1 μm or smaller, more preferably 0.05 μm or smaller, andparticularly preferably 0.01 μm or smaller. Specifically, for example,in the case of swelling synthetic mica which is a typical compound, apreferred aspect has a thickness in a range of approximately 1 nm to 50nm and a surface size (long diameter) in a range of approximately 1 μmto 20 μm.

The content of the inorganic lamellar compound is preferably in a rangeof 0% by mass to 60% by mass and more preferably in a range of 3% bymass to 50% by mass of the total solid content of the protective layer.Even in a case in which multiple kinds of inorganic lamellar compoundsare jointly used, the total amount of the inorganic lamellar compoundsis preferably the above-described content. Within the above-describedrange, the oxygen-shielding properties improve, and a favorablesensitivity can be obtained. In addition, the degradation of theink-absorbing properties can be prevented.

The protective layer may include well-known additives such as aplasticizer for imparting flexibility, a surfactant for improvingcoating properties, and inorganic particles for controlling slidingproperties on the surface. In addition, the sensitization agentdescribed in the section of the image-recording layer may be added tothe protective layer.

The protective layer is formed using a well-known coating method. Thecoating amount of the protective layer (solid content) is preferably ina range of 0.01 g/m² to 10 g/m², more preferably in a range of 0.02 g/m²to 3 g/m², and particularly preferably in a range of 0.02 g/m² to 1g/m².

(Method for Producing Lithographic Printing Plate)

A lithographic printing plate can be produced by exposing thelithographic printing plate precursor of the embodiment of the presentdisclosure in an image shape to carry out a development process.

An embodiment of a method for producing a lithographic printing plateaccording to an embodiment of the present disclosure includes anexposure step of exposing the lithographic printing plate precursoraccording to the embodiment of the present disclosure in an image shapeand forming an exposed portion and a non-exposed portion and anon-machine development step of removing the non-exposed portion bysupplying at least one of printing ink or dampening water in this order.

In addition, another embodiment of the method for producing alithographic printing plate according to the embodiment of the presentdisclosure includes an exposure step of exposing the lithographicprinting plate precursor according to the embodiment of the presentdisclosure in an image shape and forming an exposed portion and anon-exposed portion and a development step of removing the non-exposedportion by supplying a developer having pH of 2 or higher and 11 orlower in this order.

Hereinafter, regarding the method for producing a lithographic printingplate according to the embodiment of the present disclosure and alithographic printing method according to an embodiment of the presentdisclosure, preferred aspects of the respective steps will besequentially described. Meanwhile, the lithographic printing plateprecursor of the embodiment of the present disclosure can also bedeveloped using a developer.

<Exposure Step>

The method for producing a lithographic printing plate according to theembodiment of the present disclosure preferably includes an exposurestep of exposing the lithographic printing plate precursor according tothe embodiment of the present disclosure in an image shape and formingan exposed portion and a non-exposed portion. The lithographic printingplate precursor according to the embodiment of the present disclosure ispreferably exposed in an image shape by laser exposure through atransparent original image having a linear image, a halftone dot image,or the like or by laser light exposure according to digital data.

As the wavelength of a light source, a range of 750 nm to 1,400 nm ispreferably used. The light source having a wavelength in a range of 750nm to 1,400 nm is preferably a solid-state laser or a semiconductorlaser that radiates infrared rays. Regarding an infrared laser, theoutput is preferably 100 mW or more, the exposure time per pixel ispreferably 20 microseconds or shorter, and the irradiation energy amountis preferably 10 mJ/cm² to 300 mJ/cm². In addition, in order to shortenthe exposure time, a multibeam laser device is preferably used. Theexposure mechanism may be any one of an in-plane drum method, anexternal surface drum method, a flat head method, or the like.

The image exposure can be carried out using a platesetter or the likeand an ordinary method. In the case of on-machine development, imageexposure may be carried out on a printer after the lithographic printingplate precursor is mounted on the printer.

<On-Machine Development Step and Development Step>

The method for producing a lithographic printing plate according to theembodiment of the present disclosure preferably includes an on-machinedevelopment step of removing the non-exposed portion by supplying atleast one of printing ink or dampening water in this order.

In addition, the method for producing a lithographic printing plateaccording to the embodiment of the present disclosure may be carried outusing a development method using a developer (developer treatmentmethod).

For example, for the method for producing a lithographic printing plateaccording to the embodiment of the present disclosure, a developmentstep of removing the non-exposed portion by supplying a developer havingpH of 2 or higher and 11 or lower is exemplified.

Hereinafter, the on-machine development method will be described.

—On-Machine Development Method—

In the on-machine development method, a lithographic printing plate ispreferably produced by supplying oil-based ink and an aqueous componentto the lithographic printing plate precursor exposed in an image shapeon a printer and removing an image-forming layer in a non-image area.

That is, in a case in which the lithographic printing plate precursor isexposed in an image shape and then mounted as it is in a printer withoutcarrying out any development process or the lithographic printing plateprecursor is mounted in a printer, then, exposed in an image shape on aprinter, and subsequently supplied with oil-based ink and an aqueouscomponent to carry out printing, in an initial stage in the middle ofprinting, a non-cured image-forming layer in a non-image area isdissolved or dispersed by any or both of the supplied oil-based ink andaqueous component so as to be removed, and the hydrophilic surface isexposed in the removed portion. On the other hand, in an exposedportion, an image-forming layer cured by exposure forms an oil-basedink-receiving portion having a lipophilic surface. Any of the oil-basedink or the aqueous component may be supplied to the surface of the platein the beginning; however, from the viewpoint of preventing the aqueouscomponent from being contaminated by a component of the image-forminglayer from which the aqueous component is removed, the oil-based ink ispreferably supplied in the beginning. In the above-described manner, thelithographic printing plate precursor is on-machine-developed on theprinter and is used as it is for printing a number of pieces of paper.As the oil-based ink and the aqueous component, ordinary printing inkand ordinary dampening water for lithographic printing are preferablyused.

—Developer Process Method—

The lithographic printing plate precursor according to the embodiment ofthe present disclosure can be used to produce lithographic printingplates by means of a development process in which a developer is used byappropriately selecting the binder polymer and the like which are theconstituent components of the image-recording layer. Examples of thedevelopment process in which a developer is used include an aspect inwhich a developer having a pH of 2 to 11 which may contain at least onecompound selected from the group consisting of a surfactant and awater-soluble polymer compound is used (also referred to as simpledevelopment process).

In a case in which a water-soluble polymer compound is added to thedeveloper as necessary, it is possible to carry out development and thegum liquid process step at the same time. Therefore, the post waterwashing step is not particularly necessary, and it is possible to carryout the drying step after carrying out development and the gum liquidprocess in a single step using a single liquid. Therefore, thedevelopment process in which a developer is used is preferably a methodfor producing a lithographic printing plate including a step ofdeveloping the image-exposed lithographic printing plate precursor usinga developer having a pH of 2 to 11. After the development process, it ispreferable to remove the excess developer using a squeeze roller andthen dry the lithographic printing plate precursor.

That is, in the development step of the method for producing alithographic printing plate according to the embodiment of the presentdisclosure, it is preferable to carry out the development process andthe gum liquid process in a single step using a single liquid.

Carrying out the development process and the gum liquid process in asingle step using a single liquid means that the development process andthe gum liquid process are not carried out as separate steps, but thedevelopment process and the gum liquid process are carried out in asingle step using a single liquid.

The development process can be preferably carried out using means forsupplying the developer and an automatic development processorcomprising a rubbing member. The rubbing member is particularlypreferably an automatic development processor in which a rotary brushroll is used.

The number of the rotary brush rolls is preferably two or more.Furthermore, the automatic development processor preferably comprises,after the development process means, means for removing an excessdeveloper such as a squeeze roller or drying means such as a hot airdevice. In addition, the automatic development processor may comprise,before the development process means, preheating means for heating theimage-exposed lithographic printing plate precursor.

A process in the above-described automatic development processor has anadvantage that there is no need for coping with development scum derivedfrom the protective layer/an image-recording layer that is generated inthe case of so-called on-machine development process.

In the development step, in the case of a manual process, as adevelopment process method, for example, a method in which an aqueoussolution is soaked into a sponge or an absorbent cotton, thelithographic printing plate precursor is processed while rubbing theentire surface of the plate with the sponge or the absorbent cotton,and, after the end of the process, the lithographic printing plateprecursor is dried is preferably exemplified. In the case of animmersion process, for example, a method in which the lithographicprinting plate precursor is immersed in a pad or a deep tank filled withan aqueous solution and stirred for approximately 60 seconds and thendried while being rubbed with an absorbent cotton, a sponge, or the likeis preferably exemplified.

In the development process, a device having a simplified structure and asimplified step is preferably used.

In the alkali development process, the protective layer is removed bythe prior water washing step, next, development is carried out using analkaline developer having a high pH, after that, an alkali is removed inthe post water washing step, a gum process is carried out in agum-pulling step, and the lithographic printing plate precursor is driedin the drying step.

In the simple development process, it is possible to carry outdevelopment and gum pulling at the same time using a single liquid.Therefore, it becomes possible not to provide the post water washingstep and the gum process step, and it is preferable to carry outdevelopment and gum pulling (gum liquid process) using a single liquidand then carry out the drying step as necessary.

Furthermore, it is preferable to carry out the removal of the protectivelayer, development, and gum pulling at the same time using a singleliquid without carrying out the prior water washing step. In addition,it is preferable to, after development and gum pulling, remove theexcess developer using a squeeze roller and then dry the lithographicprinting plate precursor.

In the development step, a method in which the lithographic printingplate precursor is immersed in the developer once or a method in whichthe lithographic printing plate precursor is immersed in the developertwice or more may be used. Among these, a method in which thelithographic printing plate precursor is immersed in the developer onceor twice is preferred.

For the immersion, the exposed lithographic printing plate precursor maybe immersed in a developer tank filled with the developer or thedeveloper may be blown onto the plate surface of the exposedlithographic printing plate precursor by means of spraying or the like.

Meanwhile, even in the case of immersing the lithographic printing plateprecursor in the developer twice or more, a case in which thelithographic printing plate precursor is immersed twice or more in thesame developer or a developer and another developer (tired liquid) inwhich the components of the image-recording layer are dissolved ordispersed due to the development process is regarded as the developmentprocess using a single liquid (single liquid process).

In the development process, a rubbing member is preferably used, and, ina development bath for removing the non-image area of theimage-recording layer, the rubbing member such as a brush is preferablyinstalled.

The development process can be carried out according to an ordinarymethod at a temperature of preferably 0° C. to 60° C. and morepreferably 15° C. to 40° C. by, for example, immersing the exposedlithographic printing plate precursor in the developer and rubbing thelithographic printing plate precursor with a brush or drawing a processliquid prepared in an external tank using a pump, blowing the processliquid to the lithographic printing plate precursor from a spray nozzle,and rubbing the lithographic printing plate precursor with a brush. Thisdevelopment process can be continuously carried out a plurality oftimes. For example, after a developer prepared in an external tank isdrawn using a pump and blown to the lithographic printing plateprecursor from a spray nozzle, and the lithographic printing plateprecursor is rubbed with a brush, again, it is possible to blow thedeveloper from the spray nozzle and rub the lithographic printing plateprecursor with the brush. In the case of carrying out the developmentprocess using an automatic developing machine, the developer becomesmore tired due to an increase in the process amount, and thus it ispreferable to restore the process capability using a supplementaryliquid or a fresh developer.

In the development process, it is also possible to use a gum coater oran automatic developing machine that has been known in the related artfor presensitized plates (PS plates) and computer to plates (CTP). Inthe case of using an automatic developing machine, for example, it ispossible to apply any method of a method in which a developer preparedin a development tank or a developer prepared in an external tank isdrawn using a pump and blown to a lithographic printing plate precursorfrom a spray nozzle, a method in which a printing plate is immersed andtransported in a liquid in a tank filled with a developer using a guideroll or the like, or a so-called single-use process method in which onlya necessary amount of a substantially unused developer is supplied toeach plate and is processed. In any of the methods, a rubbing mechanismsuch as a brush or a moulton roller is more preferably provided. Forexample, it is possible to use commercially available automaticdeveloping machines (Clean Out Unit C85/C125, Clean-Out Unit+C85/120,FCF 85V, FCF 125V, FCF News (manufactured by Glunz & Jensen), AZURACX85, AZURA CX125, AZURA CX150 (manufactured by AGFA GRAPHICS). Inaddition, it is also possible to use a device into which a laser-exposedportion and an automatic developing machine portion are integrallycombined.

The details of components and the like of the developer that is used inthe development step will be described below.

[pH]

The pH of the developer is preferably 2 to 11, more preferably 5 to 9,and still more preferably 7 to 9. From the viewpoint of developabilityor the dispersibility of the image-recording layer, it is advantageousto set the value of pH to be high; however, regarding a printingproperty, particularly, the suppression of stain, it is effective to setthe value of pH to be low.

Here, the pH is a value that is measured at 25° C. using a pH meter(model No.: HM-31, manufactured by DKK-Toa Corporation).

[Surfactant]

The developer may contain a surfactant such as an anionic surfactant, anonionic surfactant, a cationic surfactant, or an amphoteric surfactant.

From the viewpoint of a blanket stain property, the developer preferablyincludes at least one selected from the group consisting of an anionicsurfactant and an amphoteric surfactant.

In addition, the developer preferably includes a nonionic surfactant andmore preferably includes a nonionic surfactant and at least one selectedfrom the group consisting of an anionic surfactant and an amphotericsurfactant.

As the anionic surfactant, a compound represented by Formula (I) ispreferably exemplified.

R¹—Y¹—X¹  (I)

In Formula (I), R¹ represents an alkyl group, a cycloalkyl group, analkenyl group, an aralkyl group, or an aryl group which may have asubstituent.

As the alkyl group, for example, an alkyl group having 1 to 20 carbonatoms is preferred, and, specifically, a methyl group, an ethyl group, apropyl group, an n-butyl group, a sec-butyl group, a hexyl group, a2-ethylhexyl group, an octyl group, a decyl group, a dodecyl group, ahexadecyl group, a stearyl group, and the like can be preferablyexemplified.

The cycloalkyl group may be a monocyclic cycloalkyl group or apolycyclic cycloalkyl group. As the monocyclic cycloalkyl group, amonocyclic cycloalkyl group having 3 to 8 carbon atoms is preferred, anda cyclopropyl group, a cyclopentyl group, a cyclohexyl group, or acyclooctyl group is more preferred. As the polycyclic cycloalkyl group,for example, an adamantyl group, a norbomyl group, an isobornyl group, acamphanyl group, a dicyclopentyl group, an α-pinel group, atricyclodecanyl group, and the like can be preferably exemplified.

As the alkenyl group, for example, an alkenyl group having 2 to 20carbon atoms is preferred, and, specifically, a vinyl group, an allylgroup, a butenyl group, a cyclohexenyl group, and the like can bepreferably exemplified.

As the aralkyl group, for example, an aralkyl group having 7 to 12carbon atoms is preferred, and, specifically, a benzyl group, aphenethyl group, a naphthylmethyl group, and the like can be preferablyexemplified.

As the aryl group, for example, an aryl group having 6 to 15 carbonatoms is preferred, and, specifically, a phenyl group, a tolyl group, adimethylphenyl group, a 2,4,6-trimethylphenyl group, a naphthyl group,an anthryl group, a 9,10-dimethoxyanthryl group, and the like can bepreferably exemplified.

As the substituent, monovalent non-metal atomic groups excluding ahydrogen atom are used, and preferred examples thereof include a halogenatom (F, Cl, Br, or I), a hydroxy group, an alkoxy group, an aryloxygroup, an acyl group, an amide group, an ester group, an acyloxy group,a carboxy group, a carboxylic acid anion group, a sulfonic acid aniongroup, and the like.

As specific examples of the alkoxy group in the substituent, alkoxygroups preferably having 1 to 40 carbon atoms and more preferably having1 to 20 carbon atoms such as a methoxy group, an ethoxy group, apropyloxy group, an isopropyloxy group, a butyloxy group, a pentyloxygroup, a hexyloxy group, a dodecyloxy group, a stearyloxy group, amethoxyethoxy group, a poly(ethyleneoxy) group, and a poly(propyleneoxy)group are exemplified. As the aryloxy group, aryloxy groups having 6 to18 carbon atoms such as a phenoxy group, a tolyloxy group, a xylyloxygroup, a mesityloxy group, a cumenyl oxy group, a methoxyphenyloxygroup, an ethoxyphenyloxy group, a chlorophenyloxy group, abromophenyloxy group, and a naphthyloxy group are exemplified. As theacyl group, acyl groups having 2 to 24 carbon atoms such as an acetylgroup, a propanoyl group, a butanoyl group, a benzoyl group, and anaphthoyl group are exemplified. As the amide group, amide groups having2 to 24 carbon atoms such as an acetamide group, a propionic acid amidegroup, a dodecanoic acid amide group, a palmitic acid amide group, astearic acid amide group, a benzoic acid amide group, and a naphthoicacid amide group are exemplified. As the acyloxy group, acyloxy groupshaving 2 to 20 carbon atoms such as an acetoxy group, a propanoyloxygroup, a benzoyloxy group, and a naphthoyloxy group are exemplified. Asthe ester group, ester groups having 1 to 24 carbon atoms such as amethyl ester group, an ethyl ester group, a propyl ester group, a hexylester group, an octyl ester group, a dodecyl ester group, and a stearylester group are exemplified. The substituent may be a substituent formedof a combination of two or more substituents described above.

X¹ represents a sulfonate group, a sulfuric acid monoester salt group, acarboxylate group, or a phosphate group.

Y¹ represents a single bond, —C_(n)H_(2n)—,—C_(n-m)H_(2(n-m))OC_(m)H_(2m)—, —O—(CH₂CH₂O)_(n)—,—O—(CH₂CH(CH₃)O)_(n)—, —O—(CH(CH₃)CH₂O)_(n)—, —O—(CH₂CH₂CH₂O)_(n)—,—CO—NH—, or a divalent linking group formed of a combination of two ormore thereof and satisfies n≥1 and n≥m≥0.

Among compounds represented by Formula (I), a compound represented byFormula (I-A) or (I-B) is preferred from the viewpoint of scratch stainresistance.

In Formula (I-A) and Formula (I-B), R^(A1) to R^(A10) each independentlyrepresent a hydrogen atom or an alkyl group, nA represents an integer of1 to 3, X^(A1) and X^(A2) each independently represents a sulfonategroup, a sulfuric acid monoester salt group, a carboxylate group, or aphosphate group, Y^(A1) and Y^(A2) each independently represents asingle bond, —C_(n)H_(2n)—,—C_(n-m)H_(2(n-m))OC_(m)H_(2m)—O—(CH₂CH₂O)_(n)—, —O—(CH₂CH(CH₃)O)_(n)—,—O—(CH(CH₃)CH₂O)_(n)—, —O—(CH₂CH₂CH₂O)_(m)—, —CO—NH—, or a divalentlinking group formed of a combination of two or more thereof andsatisfies n≥1 and n≥m≥0, and the total of the numbers of the carbonatoms in R^(A1) to R^(A5) or R^(A6) to R^(A10) and Y^(A1) or Y^(A2) isthree or more.

In the compound represented by Formula (I-A) or Formula (I-B), the totalnumber of carbon atoms in R^(A1) to R^(A5) and Y^(1A) or R^(A6) toR^(A10) and Y^(A2) is preferably 25 or less and more preferably 4 to 20.The structure of the above-described alkyl group may be linear orbranched.

X^(A1) and X^(A2) in the compound represented by Formula (I-A) orFormula (I-B) are preferably a sulfonate group or a carboxylate group.In addition, the salt structure in X^(A1) and X^(A2) is preferably analkali metal salt since the alkali metal salt has a favorable solubilityparticularly in water-based solvents. Among them, a sodium salt or apotassium salt is particularly preferred.

Regarding the compound represented by Formula (I-A) or Formula (I-B), itis possible to refer to the description of Paragraphs 0019 to 0037 ofJP2007-206348A.

As the anionic surfactant, it is possible to preferably use compoundsdescribed in Paragraphs 0023 to 0028 of JP2006-065321A.

The amphoteric surfactant that is used in the developer is notparticularly limited, and amine oxide-based surfactants such asalkyldimethylamine oxide, betaine-based surfactants such as alkylbetaine, aliphatic acid amidopropyl betaine, and alkyl imidazole, andamino acid-based surfactants such as sodium alkylamino aliphatic acid.

Particularly, alkyldimethylamine oxide that may have a substituent,alkylcarboxybetaine that may have a substituent, and alkyl sulfobetainethat may have a substituent are preferably used. As specific examplesthereof, a compound represented by Formula (2) in Paragraph 0256 ofJP2008-203359A, compounds represented by Formula (I), Formula (II), andFormula (VI) in Paragraphs 0028 of JP2008-276166A, and compoundsdescribed in Paragraphs 0022 to 0029 of JP2009-047927A can beexemplified.

As an amphoteric ionic surfactant that is used in the developer, acompound represented by General Formula (1) or a compound represented byGeneral Formula (2) is preferred.

In General Formulae (1) and (2), R¹ and R¹¹ each independently representan alkyl group having 8 to 20 carbon atoms or an alkyl group having alinking group having 8 to 20 carbon atoms in total.

R², R³, R¹², and R¹³ each independently represent a hydrogen atom or agroup containing an alkyl group or an ethylene oxide structure.

R⁴ and R¹⁴ each independently represent a single bond or an alkylenegroup.

In addition, two groups of R¹, R², R³, and R⁴ may be bonded to eachother to form a ring structure, and two groups of R¹¹, R¹², R¹³, and R¹⁴may be bonded to each other to form a ring structure.

In the compound represented by General Formula (1) or the compoundrepresented by General Formula (2), in a case in which the total numberof carbon atoms becomes large, a hydrophobic portion becomes large, andthe solubility in water-based developers degrades. In this case, thesolubility is improved by mixing an organic solvent such as an alcoholthat aids dissolution as a dissolution aid into water; however, in acase in which the total number of carbon atoms becomes too large, it isnot possible to dissolve the surfactant in an appropriate mixing range.Therefore, the total of the numbers of carbon atoms in R¹ to R⁴ or R¹¹to R¹⁴ is preferably 10 to 40 and more preferably 12 to 30.

The alkyl group having a linking group represented by R¹ or R¹¹represents a structure in which a linking group is present between alkylgroups. That is, in a case in which the number of linking groups is one,the alkyl group can be represented by “-an alkylene group-a linkinggroup-an alkyl group”. As the linking group, an ester bond, a carbonylbond, and an amide bond are exemplified. The number of the linkinggroups may be two or more, but is preferably one, and an amide bond isparticularly preferred. The total number of carbon atoms in the alkylenegroup that bonds to the linking group is preferably 1 to 5. Thisalkylene group may be linear or branched, but is preferably a linearalkylene group. The number of carbon atoms in the alkyl group that bondsto the linking group is preferably 3 to 19, and the alkyl group may belinear or branched, but is preferably linear alkyl group.

In a case in which R² or R¹² is an alkyl group, the number of carbonatoms is preferably 1 to 5 and particularly preferably 1 to 3. The alkylgroup may be any of linear or branched, but is preferably a linear alkylgroup.

In a case in which R³ or R¹³ is an alkyl group, the number of carbonatoms is preferably 1 to 5 and particularly preferably 1 to 3. The alkylgroup may be any of linear or branched, but is preferably a linear alkylgroup.

As the group containing an ethylene oxide structure represented by R³ orR¹³, groups represented by —R^(a)(CH₂CH₂O)_(n)R^(b) can be exemplified.Here, R^(a) represents a single bond, an oxygen atom, or a divalentorganic group (preferably having 10 or less carbon atoms), R^(b)represents a hydrogen atom or an organic group (preferably having 10 orless carbon atoms), and n represents an integer of 1 to 10.

In a case in which R⁴ or R¹⁴ is an alkylene group, the number of carbonatoms is preferably 1 to 5 and particularly preferably 1 to 3. Thealkylene group may be any of linear or branched, but is preferably alinear alkylene group.

The compound represented by General Formula (1) or the compoundrepresented by General Formula (2) preferably has an amide bond and morepreferably has an amide bond as the linking group as R¹ or R¹¹.

Representative examples of the compound represented by General Formula(1) or the compound represented by General Formula (2) will beillustrated below, but the present disclosure is not limited thereto.

The compound represented by General Formula (1) or (2) can besynthesized using a well-known method. In addition, it is also possibleto use commercially available compounds. As the commercially availableproducts of the compound represented by General Formula (1), SOFTAZOLINELPB, SOFTAZOLINE LPB-R, and BISTA MAP manufactured by Kawaken FineChemicals Co., Ltd., TAKESURF C-157L manufactured by Takemoto Oil & FatCo., Ltd., and the like are exemplified. As the commercially availableproducts of the compound represented by General Formula (2), SOFTAZOLINELAO manufactured by Kawaken Fine Chemicals Co., Ltd., AMOGEN AOLmanufactured by DKS Co., Ltd., and the like are exemplified.

In the developer, one amphoteric ionic surfactant may be used singly ortwo or more amphoteric ionic surfactants may be used in combination.

As nonionic surfactant, polyoxyethylene alkyl ethers, polyoxyethylenealkyl phenyl ethers, polyoxyethylene polystyryl phenyl ether, glycerinaliphatic acid partial esters, sorbitan aliphatic acid partial esters,pentaerythritol aliphatic acid partial esters, propylene glycol monoaliphatic acid ester, sucrose aliphatic acid partial ester,polyoxyethylene sorbitan aliphatic acid partial esters, polyoxyethylenesorbitol aliphatic acid partial esters, polyethylene glycol aliphaticacid esters, polyglycerin aliphatic acid partial esters, polyoxyethyleneglycerin aliphatic acid partial esters, polyoxyethylene diglycerins,aliphatic acid diethanolamides, N,N-bis-2-hydroxyalkylamines,polyoxyethylene alkylamine, triethanolamine aliphatic acid ester,trialkylamine oxide, polyoxyethylene alkyl phenyl ethers,polyoxyethylene-polyoxypropylene blocked copolymers, and the like areexemplified.

In addition, acetylene glycol-based and acetylene alcohol-basedoxyethylene adducts and fluorine-based and other surfactants can also beused in the same manner. Two or more surfactants described above can bejointly used.

As the nonionic surfactant, a nonionic aromatic ether-based surfactantrepresented by Formula (N1) is particularly preferably exemplified.

X^(N)—Y^(N)—O-(A¹)_(nB)-(A²)_(mB)—H  (N1)

In the formula, X^(N) represents an aromatic group that may have asubstituent, Y^(N) represents a single bond or an alkylene group having1 to 10 carbon atoms, A¹ and A² are mutually different groups and arerepresented by any of —CH₂CH₂O— or —CH₂CH(CH₃)O—, nB and mB eachindependently represent an integer of 0 to 100; here, nB and mB are notzero at the same time, and, in a case in which any of nB or mB is zero,nB and mB are not one.

In the formula, as the aromatic group as X^(N), a phenyl group, anaphthyl group, an anthranyl group, and the like are exemplified. Thesearomatic groups may have a substituent. As the substituent, organicgroups having 1 to 100 carbon atoms are exemplified. Meanwhile, in theformula, in a case in which both A and B are present, the surfactant maybe a random or blocked copolymer.

As specific examples of the organic group having 1 to 100 carbon atoms,aliphatic hydrocarbon groups and aromatic hydrocarbon groups which maybe saturated or unsaturated and may be linear or branched, for example,an alkyl group, an alkenyl group, an alkynyl group, an aryl group, anaralkyl group, and the like, additionally, an alkoxy group, an aryloxygroup, an N-alkylamino group, an N,N-dialkylamino group, an N-arylaminogroup, an N,N-diarylamino group, an N-alkyl-N-arylamino group, anacyloxy group, a carbamoyloxy group, an N-alkylcarbamoyloxy group, anN-arylcarbamoyloxy group, an N,N-dialkylcarbamoyloxy group, anN,N-diarylcarbamoyloxy group, an N-alkyl-N-arylcarbamoyloxy group, anacylamino group, an N-alkylacylamino group, an N-arylacylamino group, anacyl group, an alkoxycarbonylamino group, an alkoxycarbonyl group, anaryloxycarbonyl group, a carbamoyl group, an N-alkylcarbamoyl group, anN,N-dialkylcarbamoyl group, an N-arylcarbamoyl group anN,N-diarylcarbamoyl group, an N-alkyl-N-arylcarbamoyl group, apolyoxyalkylene chain, the above-described organic groups to which apolyoxyalkylene chain bonds, and the like. The alkyl group may be linearor branched.

In addition, as the nonionic surfactant, it is possible to preferablyuse compounds described in Paragraphs 0030 to 0040 of JP2006-065321A.

The cationic surfactant is not particularly limited, and well-knowncationic surfactants in the related art can be used. For example,alkylamine salts, quaternary ammonium salts, alkylimidazolinium salts,polyoxyethylene alkylamine salts, polyethylene polyamine derivatives,and the like are exemplified.

The surfactant may be used singly or two or more surfactants may bejointly used.

The content of the surfactant is preferably 1% by mass to 25% by mass,more preferably 2% by mass to 20% by mass, still more preferably 3% bymass to 15% by mass, and particularly preferably 5% by mass to 10% bymass of the total mass of the developer. In a case in which the contentof the surfactant is in the above-described range, the scratch stainresistance is superior, the dispersibility of development scum isexcellent, and the ink-absorbing property of lithographic printingplates to be obtained is excellent.

[Water-Soluble Polymer Compound]

From the viewpoint of adjusting the viscosity of the developer andprotecting the plate surface of a lithographic printing plate to beobtained, the developer may include a water-soluble polymer.

As a water-soluble polymer, the developer may contain a water-solublepolymer compound such as a soy polysaccharide, modified starch, gumarabic, dextrin, a fibrin derivative (for example, carboxymethylcellulose, carboxyethyl cellulose, methyl cellulose, or the like) and amodified product thereof, pullulan, polyvinyl alcohol and a derivativethereof, polyvinyl pyrrolidone, polyacrylamide and an acrylamidecopolymer, a vinyl methyl ether/maleic anhydride copolymer, a vinylacetate/maleic anhydride copolymer, or a styrene/maleic anhydridecopolymer.

As the soy polysaccharide, soy polysaccharides known in the related artcan be used, and, for example, as commercially available products, thereis SOYAFIBE (trade name, manufactured by Fuji Oil Co., Ltd.), and it ispossible to use a variety of grades of soy polysaccharides. Soypolysaccharides that can be preferably used have a viscosity of a 10% bymass aqueous solution in a range of 10 mPa·s to 100 mPa·s.

As the modified starch, starch represented by Formula (III) ispreferred. As the starch represented by Formula (III), any starch suchas corn, potato, tapioca, rice, or wheat can be used. The starch can bemodified using a method in which starch is decomposed using an acid, anenzyme, or the like to the number of glucose residues per molecule in arange of 5 to 30 and, furthermore, oxypropylene is added thereto in analkali.

In the formula, the degree of etherification (degree of substitution) isin a range of 0.05 to 1.2 per glucose unit, n represents an integer of 3to 30, and m represents an integer of 1 to 3.

Among water-soluble polymer compounds, soy polysaccharides, modifiedstarch, gum Arabic, dextrin, carboxymethyl cellulose, polyvinyl alcohol,and the like are particularly preferred.

Two or more water-soluble polymer compounds can be jointly used.

In a case in which the developer includes a water-soluble polymercompound, the content of the water-soluble polymer compound ispreferably 3% by mass or less and more preferably 1% by mass or less ofthe total mass of the developer. In the above-described aspect, theviscosity of the developer is appropriate, and it is possible tosuppress the deposition of development scum or the like in a rollermember such as an automatic developing machine.

[Other Additives]

The developer that is used in the present disclosure may contain, inaddition to the above-described components, a wetting agent, apreservative, a chelate compound, a defoamer, an organic acid, anorganic solvent, an inorganic acid, an inorganic salt, or the like.

As the wetting agent, ethylene glycol, propylene glycol, triethyleneglycol, butylene glycol, hexylene glycol, diethylene glycol, dipropyleneglycol, glycerin, trimethylolpropane, diglycerin, and the like arepreferably used. The wetting agent may be used singly or two or morewetting agents may be jointly used. The content of the wetting agent ispreferably 0.1% by mass to 5% by mass of the total mass of thedeveloper.

As the preservative, phenol or a derivative thereof, formalin, animidazole derivative, sodium dehydroacetate, a 4-isothiazolin-3-onederivative, benzisothiazolin-3-one, 2-methyl-4-isothiazolin-3-one, abenzotriazole derivative, an amidine guanidine derivative, a quaternaryammonium salt, a derivative of pyridine, quinoline, guanidine, or thelike, diazine, a triazole derivative, oxazole, an oxazine derivative,nitrobromo alcohol-based 2-bromo-2-nitropropane-1,3-diol,1,1-dibromo-1-nitro-2-ethanol, 1,1-dibromo-1-nitro-2-propanol, or thelike can be preferably used.

The amount of the preservative added needs to be an amount in which thepreservative stably exhibits an effect with respect to bacteria, fungi,yeast, and the like and which varies depending on the kind of bacteria,fungi, and yeast and is preferably in a range of 0.01% by mass to 4% bymass of the total mass of the developer. In addition, two or morepreservatives are preferably jointly used so as to be effective to avariety of fungi and bacteria.

As the chelate compound, for example, ethylenediaminetetraacetic acid,potassium salts thereof, and sodium salts thereof;diethylenetriaminepentaacetic acid, potassium salts thereof, and sodiumsalts thereof; triethylenetetraminehexaacetic acid, potassium saltsthereof, and sodium salts thereof; hydroxyethylethylenediaminetriaceticacid, potassium salts thereof; and sodium salts thereof;nitrilotriacetic acid, and sodium salts thereof;1-hydroxyethane-1,1-diphosphonic acid, potassium salts thereof, andsodium salts thereof; and organic phosphonic acids such asaminotri(methylene phosphonate), potassium salts thereof, and sodiumsalts thereof can be exemplified. Instead of sodium salts and potassiumsalts of chelating agents, salts of organic amines are also effective.

The chelating agent is preferably a chelating agent that is stablypresent in a process liquid composition and does not impair a printingproperty. The content of the chelating agent is preferably 0.001% bymass to 1.0% by mass of the total mass of the developer.

As the defoamer, it is possible to use an ordinary silicone-basedself-emulsification-type, emulsification-type, or nonionic compoundhaving a hydrophilic-lipophilic balance (HLB) of 5 or less. A siliconedefoamer is preferred.

Meanwhile, a silicone-based surfactant is regarded as the defoamer.

The content of the defoamer is preferably in a range of 0.001% by massto 1.0% by mass of the total mass of the developer.

As the organic acid, citric acid, acetic acid, oxalic acid, malonicacid, salicylic acid, caprylic acid, tartaric acid, malic acid, lacticacid, levulinic acid, p-toluenesulfonic acid, xylenesulfonic acid,phytic acid, organic phosphonic acid, and the like are exemplified. Theorganic acid can also be used in a form of an alkali metal salt orammonium salt thereof. The content of the organic acid is preferably0.01% by mass to 0.5% by mass of the total mass of the developer.

As the organic solvent, for example, aliphatic hydrocarbons (hexane,heptane, “ISOPAR E, H, G” (manufactured by Esso Chemical Co., Ltd.) andthe like), aromatic hydrocarbons (toluene, xylene, and the like),halogenated hydrocarbons (methylene dichloride, ethylene dichloride,trichloroethylene, monochlorobenzene, and the like), polar solvents, andthe like are exemplified.

As the polar solvents, alcohols (methanol, ethanol, propanol,isopropanol, benzyl alcohol, ethylene glycol monomethyl ether,2-ethoxyethanol, diethylene glycol monoethyl ether, diethylene glycolmonohexyl ether, triethylene glycol monomethyl ether, propylene glycolmonoethyl ether, propylene glycol monomethyl ether, polyethylene glycolmonomethyl ether, polypropylene glycol, tetraethylene glycol, ethyleneglycol monobutyl ether, ethylene glycol monobenzyl ether, ethyleneglycol monophenyl ether, methyl phenyl carbinol, n-amyl alcohol, methylamyl alcohol, and the like), ketones (acetone, methyl ethyl ketone,ethyl butyl ketone, methyl isobutyl ketone, cyclohexanone, and thelike), esters (ethyl acetate, propyl acetate, butyl acetate, amylacetate, benzyl acetate, methyl lactate, butyl lactate, ethylene glycolmonobutyl acetate, propylene glycol monomethyl ether acetate, diethyleneglycol acetate, diethyl phthalate, butyl levulinate, and the like),other polar solvents (triethyl phosphate, tricresyl phosphate,N-phenylethanolamine, N-phenyldiethanolamine, and the like), and thelike are exemplified.

In a case in which the organic solvent is not soluble in water, it isalso possible to make the organic solvent soluble in water using asurfactant or the like and then use the organic solvent, and, in a casein which the developer contains the organic solvent, from the viewpointof safety and inflammability, the concentration of the solvent in thedeveloper is preferably less than 40% by mass.

As the inorganic acid and the inorganic salt, phosphoric acid,metaphosphoric acid, primary ammonium phosphate, secondary ammoniumphosphate, primary sodium phosphate, secondary sodium phosphate, primarypotassium phosphate, secondary potassium phosphate, sodiumtripolyphosphate, potassium pyrophosphate, sodium hexametaphosphate,magnesium nitrate, sodium nitrate, potassium nitrate, ammonium nitrate,sodium sulfate, potassium sulfate, ammonium sulfate, sodium sulfite,ammonium sulfite, sodium hydrogen sulfate, nickel sulfate, and the likeare exemplified. The content of the inorganic salt is preferably 0.01%by mass to 0.5% by mass of the total mass of the developer.

The developer is prepared by dissolving or dispersing the respectivecomponents described above in water as necessary. The concentration ofthe solid content of the developer is preferably 2% by mass to 25% bymass. As the developer, it is also possible to produce a concentratedliquid and, at the time of being used, dilute the concentrated liquidwith water.

The developer is preferably an aqueous developer.

From the viewpoint of the dispersibility of development scum, thedeveloper preferably contains an alcohol compound.

As the alcohol compound, methanol, ethanol, propanol, isopropanol,benzyl alcohol, and the like are exemplified. Among these, benzylalcohol is preferred.

The content of the alcohol compound is preferably 0.01% by mass to 5% bymass, more preferably 0.1% by mass to 2% by mass, and particularlypreferably 0.2% by mass to 1% by mass of the total mass of the developerfrom the viewpoint of the dispersibility of development scum.

<Printing Step>

The lithographic printing method according to an embodiment of thepresent disclosure includes a printing step of printing a recordingmedium by supplying printing ink to the lithographic printing platedeveloped in the on-machine development step or the development step.

The printing ink is not particularly limited, and a variety ofwell-known inks can be used as desired. In addition, as the printingink, oil-based ink or ultraviolet-curable ink (UV ink) is preferablyexemplified, and UV ink is more preferably exemplified.

In addition, in the printing step, dampening water may be supplied asnecessary.

In addition, the printing step may be successively carried out after theon-machine development step without stopping the printer.

The recording medium is not particularly limited, and a well-knownrecording medium can be used as desired.

In the method for producing the lithographic printing plate from thelithographic printing plate precursor according to the embodiment of thepresent disclosure and the lithographic printing method according to theembodiment of the present disclosure, the full surface of thelithographic printing plate precursor may be heated as necessary beforeexposure, in the middle of exposure, or during a period of time fromexposure to development. Such heating accelerates an image-formingreaction in the image-forming layer and generates an advantage of theimprovement in sensitivity or printing resistance, the stabilization ofsensitivity, or the like. Heating before development is preferablycarried out in a mild condition of 150° C. or lower. In theabove-described aspect, it is possible to prevent a problem of thecuring of the non-image area. For heating after development, anextremely strong condition is preferably used, and a range of 100° C. to500° C. is preferred. In the above-described range, a sufficientimage-strengthening action is obtained, and it is possible to suppress aproblem of the deterioration of the support or the thermal decompositionof the image area.

(Polymer Particle)

A polymer particle according to an embodiment of the present disclosureincludes an addition polymerization-type resin having a hydrophilicstructure and a crosslinking structure.

The polymer particle according to the embodiment of the presentdisclosure is identical to the polymer particle that is contained in theimage-recording layer of the above-described lithographic printing plateprecursor, and a preferred aspect thereof is also identical thereto.

(Composition)

A composition according to an embodiment of the present disclosureincludes the polymer particle according to the embodiment of the presentdisclosure.

In addition, the composition according to the embodiment of the presentdisclosure preferably further includes an infrared absorber, apolymerization initiator, and a polymerizable compound. In theabove-described aspect, the composition can be preferably used as aphotosensitive composition and can be preferably used to form theimage-recording layer in the lithographic printing plate precursoraccording to the embodiment of the present disclosure.

The infrared absorber, the polymerizable compound, and thepolymerization initiator that are included in the composition accordingto the embodiment of the present disclosure are respectively identicalto the infrared absorber, the polymerizable compound, and thepolymerization initiator that are included in the image-recording layerof the above-described lithographic printing plate precursor.

In addition, the composition according to the embodiment of the presentdisclosure may further contain at least one selected from the groupconsisting of the binder polymer, the radical production aid, the chaintransfer agent, the additional polymer particle, thelow-molecular-weight hydrophilic compound, the sensitization agent, theacid color developing agent, and a well-known solvent.

The contents of the respective components included in the compositionaccording to the embodiment of the present disclosure correspond to thecontents of the respective components included in the image-recordinglayer of the above-described lithographic printing plate precursor readas the amounts of solid contents in the composition.

In the case of using the composition according to the embodiment of thepresent disclosure, it is possible to preferably obtain lithographicprinting plate precursors.

EXAMPLES

Hereinafter, the present disclosure will be described in detail usingexamples, but the present disclosure is not limited thereto. Meanwhile,in the present examples, unless particularly otherwise described, “%”and “parts” respectively refer to “% by mass” and “parts by mass”.Meanwhile, for polymer compounds, unless particularly otherwisedescribed, the molecular weight refers to the weight-average molecularweight (Mw), and the ratio of a constituent repeating unit is the molarpercentage. In addition, the weight-average molecular weight (Mw) is avalue measured as a polystyrene equivalent value using the gelpermeation chromatography (GPC) method. In addition, unless particularlyotherwise described, the average particle diameter refers to thevolume-average particle diameter.

Meanwhile, polymer particles G-1 to G-21 used in the examples arerespectively the same as the above-described polymer particles G-1 toG-21.

<Synthesis of Polymer Particle G-1>

A compound (1) (10.8 g), a compound (2) (33.0 g), a compound (3) (10.0g), a compound (4) (2.0 g), and distilled water (950 g) were added to athree-neck flask, stirred in a nitrogen atmosphere, and heated to 70° C.Next, potassium persulfate (1.9 g) was added thereto and stirred forfive hours. After that, the components were heated to 95° C. and stirredfor two hours. A reaction liquid was cooled to room temperature (25° C.,which shall apply below), thereby obtaining a dispersion liquid (solidcontent: 5%) of a polymer particle G-1. The average particle diameter ofthe polymer particle G-1 was 180 nm.

<Syntheses of Polymer Particles G-2 to 21 and G′-1, 2, and 4>

Polymer particles G-2 to 21 and G′-1, 2, and 4 were also synthesized inthe same manner using the same method as in the synthesis of the polymerparticle G-1 except for the fact that the monomers serving as rawmaterials and the amounts of the monomers used were changed.

Meanwhile, the polymer particles G-2 to 21 were particles having thestructures illustrated above, and the polymer particles G′-1 and 2 wereparticles having structures illustrated below. In addition, the averageparticle diameter of the polymer particle G′-1 was 180 nm.

<Synthesis of Polymer Particle G′-3>

As oil-phase components, isophorone diisocyanate (4 g),trimethylolpropane (6 molar equivalent), and xylene diisocyanate (18molar equivalent) were added, and an adduct obtained by adding methylsingle-terminated polyoxyethylene (1 molar equivalent; meanwhile, thenumber of times of repetition of an oxyethylene unit was 90) to theabove-described components (manufactured by Mitsui Chemicals Inc.; 50%by mass ethyl acetate solution) (2 g), pentaerythritol triacrylate(manufactured by Nippon Kayaku Co., Ltd., SR444) (3.15 g), and asurfactant PIONINE A-41C (manufactured by Takemoto Oil & Fat Co., Ltd.)(0.1 g) were dissolved in ethyl acetate (17 g). As a water-phasecomponent, a 4% by mass aqueous solution of polyvinyl alcohol (PVA-205manufactured by Kuraray Co., Ltd.) (40 g) was prepared. The oil-phasecomponents and the water-phase component were mixed together andemulsified using a homogenizer at 12,000 rpm for 10 minutes. Theobtained emulsified substance was added to a mixed aqueous solution ofdistilled water (25 g) and U-CAT SA102 (1,8-diazabicyclo[5.4.0]undeca-7-ene octylate, manufactured by San-Apro Ltd.) (0.2 g), stirredat room temperature for 30 minutes, and then left to stand at 45° C. for24 hours. A micro gel liquid obtained as described above was dilutedusing distilled water so that the concentration of the solid contentreached 15% by mass and was regarded as a polymer particle G′-3. Theaverage particle diameter of the polymer particle G′-3 was 260 nm.

Meanwhile, the polymer particle G′-3 is a urethane resin for which thefollowing compound is polycondensed.

<Evaluation of Dispersion Stability of Polymer Particle>

The dispersion status of a solid content of a mixed solution obtained byadding the obtained dispersion liquid of the polymer particle (1 mL) toindividual solvents (methyl ethyl ketone (MEK)/1-methoxy-2-propanol(MFG)=50/50% by mass and distilled water) (100 mL), stirring the mixturefor 10 minutes or longer, and then leaving the mixed solution to standat 20° C. for one hour was visually evaluated. The evaluation indexes ofdispersibility are as described below. A is the highest evaluation, theevaluation becomes worse in an order of A, B, C, and D, and D is thelowest evaluation.

A: A state in which there is no precipitate and dispersibility isfavorable.

B: A state in which there is a small amount of a precipitate, but theprecipitate can be easily re-dispersed.

C: A state in which there is a large amount of a precipitate, but theprecipitate can be re-dispersed.

D: A state in which there is a precipitate or an adhered substance andthe precipitate or the adhered substance cannot be re-dispersed.

TABLE 1 Evaluation of dispersion stability MEK/MFG = Polymer particle50/50% by mass Distilled water G-1 A A G-2 A A G-3 A C G-4 A A G-5 A AG-6 C A G-7 B C G-8 A B G-9 A B G-10 A B G-11 A B G-12 A A G-13 C B G-14B A G-15 A B G-16 B C G-17 C B G-18 A A G-19 A B G-20 A C G-21 C B G′-1A A G′-2 D D G′-3 A C G′-4 D C

<Production of Support 1>

In order to remove rolling oil on the surface of a 0.3 mm-thick aluminumplate (material JIS A 1050), a defatting process was carried out thereonusing a 10% by mass aqueous solution of sodium aluminate at 50° C. for30 seconds, and then the surface of the aluminum plate was grained usingthree implanted nylon brushes having a hair diameter of 0.3 mm and asuspension of pumice having a median diameter of 25 μm and water(specific gravity: 1.1 g/cm³) and well washed with water. The aluminumplate was etched by being immersed in a 25% by mass aqueous solution ofsodium hydroxide at 45° C. for nine seconds, was washed with water,then, was further immersed in a 20% by mass aqueous solution of nitricacid at 60° C. for 20 seconds, and was washed with water. The etchedamount of the grained surface was approximately 3 g/m².

Next, an electrochemical roughening process was continuously carried outthereon using an alternating current voltage of 60 Hz. An electrolyticsolution was a 1% by mass aqueous solution of nitric acid (including0.5% by mass of aluminum ions.), and the liquid temperature was 50° C.The electrochemical roughening process was carried out thereon using analternating current power supply waveform in which the time TP taken forthe current value to reach the peak from zero was 0.8 msec and the dutyratio was 1:1, and the electrochemical roughening process was carriedout using a trapezoidal rectangular wave alternating current and acarbon electrode as a counter electrode. As an auxiliary anode, ferritewas used. The current density was 30 A/dm² in terms of the peak value ofthe current, and 5% of the current coming from the power supply wasdivided into the auxiliary anode. Regarding the quantity of electricityduring nitric acid electrolysis, the quantity of electricity was 175C/dm² in a case in which the aluminum plate served as the positiveelectrode. After that, the plate was washed with water by means ofspraying.

Subsequently, an electrochemical roughening process was carried outthereon using the same method as nitric acid electrolysis in a 0.5% bymass aqueous solution of hydrochloric acid (including 0.5% by mass ofaluminum ions.) and an electrolytic solution having a liquid temperatureof 50° C. under a condition of the quantity of electricity of 50 C/dm²in a case in which the aluminum plate served as the positive electrode,and then, the plate was washed with water by means of spraying.

Next, 2.5 g/m² of a direct current anodized film was formed on thealuminum plate at a current density of 15 A/dm² using a 15% by massaqueous solution of sulfuric acid (including 0.5% by mass of aluminumions.) having a liquid temperature of 54° C. as an electrolytic solutionand then washed with water and dried. The average pore diameter of thesurface layer of the anodized film (surface average pore diameter) was10 nm.

The pore diameter of the surface layer of the anodized film was measuredusing a method in which the surface was observed an ultrahigh resolutionSEM (S-900 manufactured by Hitachi, Ltd.) at a relatively lowacceleration voltage of 12 V at a magnification of 150,000 times withoutcarrying out a vapor deposition process or the like for impartingconductive properties, 50 pores were randomly extracted, and the averagevalue was obtained. The standard error was ±10% or less.

After that, in order to ensure the hydrophilicity of a non-image area, asilicate process was carried out by dipping the support in a 2.5% bymass aqueous solution of No. 3 sodium silicate at 50° C. for sevenseconds, and the support was washed with water by means of spraying,thereby producing a support 1. The attached amount of Si was 11 mg/m².

<Preparation of Coating Fluid for Undercoat Layer>

-   -   Polymer (UC-1) [the following structure]: 0.18 parts    -   Hydroxyethyl iminodiacetic acid: 0.10 parts    -   Water: 61.4 parts

<Preparation of Coating Fluid for Protective Layer>

-   -   Inorganic lamellar compound dispersion liquid (1) [illustrated        below] 1.5 parts    -   Six percent by mass aqueous solution of polyvinyl alcohol (CKS50        manufactured by The Nippon Synthetic Chemical Industry Co.,        Ltd., sulfonic acid-modified, degree of saponification: 99% by        mol or higher, degree of polymerization: 300) 0.55 parts    -   Six percent by mass aqueous solution of polyvinyl alcohol        (PVA-405 manufactured by Kuraray Co., Ltd., degree of        saponification: 81.5 mol %, degree of polymerization: 500) 0.03        parts    -   One percent by mass aqueous solution of a surfactant        (polyoxyethylene lauryl ether, EMALEX 710, manufactured by Nihon        Emulsion Co., Ltd.) 0.86 parts    -   Ion exchange water 6.0 parts

A method for preparing the inorganic lamellar compound dispersion liquid(1) using the coating fluid for a protective layer will be describedbelow.

—Preparation of Inorganic Lamellar Compound Dispersion Liquid (1)—

Synthetic mica (SOMASIF ME-100 manufactured by Co-op Chemical Co., Ltd.)(6.4 g) was added to ion exchange water (193.6 g) and dispersed using ahomogenizer until the average particle diameter (laser scatteringmethod) reached 3 μm. The aspect ratio of the obtained dispersedparticle was 100 or higher.

<Preparation of Coating Fluid for Image-Recording Layer>

Individual components were added according to the amounts used shown inTable 2, a solvent was added thereto so that the concentration of thesolid content reached 7.0% by mass, and the components were mixedtogether. The amounts (parts) of individual materials added in Table 2or 3 are the amounts of solid contents.

Meanwhile, a coating fluid for an image-recording layer including apolymer particle was prepared by mixing and stirring a photosensitiveliquid containing components shown in Table 2 or Table 3 other than thepolymer particle in a mixed state and a polymer particle dispersionliquid immediately before the application so as to obtain a compositionshown in Table 2 or Table 3.

An expression such as “M-4/M-5 146/78” in Table 2 or Table 3 indicatesthat 146 parts of a compound M-4 and 78 parts by a compound M-5 areincluded.

Examples 1 to 21 and Comparative Examples 1 to 4

<Production of Lithographic Printing Plate Precursors>

Lithographic printing plate precursors of Examples 1 to 21 andComparative Examples 1 to 4 were respectively produced using thefollowing method.

The coating fluid for an undercoat layer having the above-describedcomposition was applied onto the support 1 so that the dried coatingamount reached 20 mg/m², thereby forming an undercoat layer. Eachcoating fluid for an image-recording layer shown in Table 2 or Table 3was applied onto the undercoat layer by means of bar coating and driedin an oven at 120° C. for 40 seconds, thereby forming an image-recordinglayer having a dried coating amount of 1.0 g/m².

The coating fluid for an image-recording layer was prepared by mixingand stirring the polymer particle immediately before the application.

As necessary, the coating fluid for a protective layer having theabove-described composition was applied onto the image-recording layerby means of bar coating and dried in an oven at 120° C. for 60 seconds,thereby forming a protective layer having a dried coating amount of 0.15g/m²

Examples in which the protective layer was formed have an expression of“Present” in the “Protective layer” column in Table 2 or Table 3.

<Evaluation of Lithographic Printing Plate Precursor>

The lithographic printing plate precursors produced as described abovewere exposed (to an equivalent irradiation energy of 110 mJ/cm²) usingMagnus 800 Quantum equipped with an infrared semiconductor lasermanufactured by Kodak Japan Ltd. under conditions of an output of 27 W,an external surface drum rotation speed of 450 rpm, and a resolution of2,400 dpi (dots per inch, 1 inch is equal to 2.54 cm). Exposed imageswere provided with a solid image and an amplitude modulation screen (AMscreen) 3% halftone dot chart.

(1) On-Machine Developability

The obtained exposed precursor was attached to a cylinder of a mediumoctavo paper-size printer SX-74 manufactured by HeidelbergerDruckmaschinen AG without being developed. To the present printer, a 100L-capacity dampening water circulation tank having a non-woven fabricfilter and a temperature control device was connected. Dampening water(80 L) containing 2.0% of dampening water S-Z1 (manufactured by FujifilmCorporation) was prepared in a circulation device, T&K UV OFS K-HS blackGE-M (manufactured by T&K TOKA Co., Ltd.) was used as printing ink,dampening water and ink were supplied using a standard automaticprinting start method, and then printing was carried out on 500 piecesof TOKUBISHI art paper (76.5 kg) at a printing rate of 10,000 pieces perhour.

The number of pieces of printing paper required until a state in whichthe ink was no longer transferred to a non-image area was formed wasmeasured as on-machine development. The measurement results are shown inTable 2 and Table 3. In Table 3, an expression of “100 pieces or more”indicates that development was not possible at a point in time where the100^(th) printing paper was used.

(2) Printing Resistance

After the on-machine developability were evaluated, printing was furthercontinued. As the number of pieces of printed paper increased, the imagearea gradually wore, and thus the ink density on printed mattersdecreased. The number of pieces of paper printed until the value of thehalftone dot area ratio of AM screen 3% halftone dots on a printedmatter measured using a gretag density meter (manufactured byGretagMacbeth) decreased to be 1% lower than the measurement valueobtained from the 500^(th) piece of printed paper was used as the numberof pieces of completely printed paper to evaluate the printingresistance. The printing resistance was evaluated using relativeprinting resistance for which the value obtained in a case in which thenumber of pieces of printed paper reached 50,000 was considered as 100.As the numerical value increase, the printing resistance becomes morefavorable. The evaluation results are shown in Table 2 and Table 3. InTable 3, an expression of “Cannot be evaluated” indicates that theon-machine development of the lithographic printing plate precursor wasnot possible and the evaluation of the printing resistance was notpossible.

Relative printing resistance=(number of pieces of printed paper ofsubject lithographic printing plate precursor)/50,000×100

(3) On-Machine Development Scum Suppression Property

After printing was carried out in the evaluation of the printingresistance as described above, the attachment status of the removed gason a form dampening roller was evaluated at the same time. The indexesare as described below. The evaluation results are shown in Table 2 orTable 3.

A: No gas is observed on the form dampening roller.

B: Gas is slightly observed on the form dampening roller.

C: Gas is significantly observed on the form dampening roller.

TABLE 2 Coating fluid for image-recording layer Acid Polymer BinderPolymerizable Polymerization Infrared Radical color-developingHydrophilic particle polymer compound initiator absorber production aidagent compound (parts) (parts) (parts) (parts) (parts) (parts) (parts)(parts) Example 1 G-1 B-1 M-4/M-5 I-1 K-3 R-1 H-1 T-1/T-3 468 179 146/78132 58 57 58 20/30 Example 2 G-2 B-1 M-1/M-2 I-1 K-1 R-1 H-3 T-1 453 156123/101 135 50 49 55 20 Example 3 G-3 B-1 M-1/M-2 I-1 K-1 R-1 H-3 T-1453 156 123/101 135 50 49 55 20 Example 4 G-4 B-1 M-2/M-3/M-4 I-1 K-1R-1 H-1 T-1/T-3 556 181 77/75/69 125 53 51 50 15/30 Example 5 G-5 B-1M-2/M-3/M-4 I-1 K-1 R-1 H-1 T-1/T-3 556 181 77/75/69 125 53 51 50 15/30Example 6 G-6 B-1 M-2/M-3/M-4 I-1 K-1 R-1 H-1 T-1/T-3 556 181 77/75/69125 53 51 50 15/30 Example 7 G-7 — M-3/M-4/M-5 I-2 K-2 R-1 H-3 T-3 350 094/41/96 58 18 87 48 75 Example 8 G-8 B-1 M-1/M-5 I-3 K-3 R-1 H-2T-1/T-2/T-3 489 163 88/103 125 49 60 65 10/10/10 Example 9 G-9 B-1M-1/M-5 I-3 K-3 R-1 H-2 T-1/T-2/T-3 489 163 88/103 125 49 60 65 10/10/10Example 10 G-10 B-1 M-1/M-5 I-3 K-3 R-1 H-2 T-1/T-2/T-3 489 163 88/103125 49 60 65 10/10/10 Example 11 G-11 B-1 M-1/M-5 I-3 K-3 R-1 H-2T-1/T-2/T-3 489 163 88/103 125 49 60 65 10/10/10 Example 12 G-12 B-1M-1/M-4/M-5 I-2 K-1 R-1 H-4 T-1/T-3 386 151 68/120/36 201 21 5 41 10/30Example 13 G-13 B-1 M-1 I-1 K-1/K-2 R-1 H-1 T-1/T-3 241 213 213 15125/25 9 33 10/25 Example 14 G-14 B-1 M-2 I-2 K-2 — H-1/H-2 T-1/T-3 190165 253 178 89 0 23/24 20/20 Example 15 G-15 B-1 M-3 I-1/I-2 K-3 R-1 H-4T-2 669 112 196 51/53 15 11 23 5 Coating fluid for image-recording layerEvaluation results Sensitization On-machine On-machine agent SurfactantSolvent Protective developability Printing development scum (parts)(parts) (mass ratio) layer (number of pieces) resistance suppressionproperty Example 1 — W-1 S-1/S-2/S-3 Absent 11 90 A 0 4 60/30/10 Example2 C-1/C-2/C-3 W-1 S-1/S-2/S-3 Present 11 87 A 25/23/30 4 50/40/10Example 3 C-1/C-2/C-3 W-1 S-1/S-2/S-3 Present 15 79 B 25/23/30 450/40/10 Example 4 C-1/C-3 W-1 S-1/S-2/S-3 Present 11 85 A 27/27 455/30/15 Example 5 C-1/C-3 W-1 S-1/S-2/S-3 Present 14 81 A 27/27 455/30/15 Example 6 C-1/C-3 W-1 S-1/S-2/S-3 Present 18 77 B 27/27 455/30/15 Example 7 — — S-4/S-5 Absent 12 78 B 0 0 80/20 Example 8C-1/C-2/C-3 W-1 S-1/S-2/S-3 Present 13 88 A 15/13/25 4 70/20/10 Example9 C-1/C-2/C-3 W-1 S-1/S-2/S-3 Present 13 83 A 15/13/25 4 70/20/10Example 10 C-1/C-2/C-3 W-1 S-1/S-2/S-3 Present 13 80 A 15/13/25 470/20/10 Example 11 C-1/C-2/C-3 W-1 S-1/S-2/S-3 Present 13 76 A 15/13/254 70/20/10 Example 12 C-1/C-2/C-3 W-1 S-1/S-2/S-3 Absent 11 73 A 5/5/5 340/40/20 Example 13 — W-1 S-1/S-2/S-3 Present 15 86 B 0 2 40/30/30Example 14 C-1/C-2/C-3 W-1 S-1/S-2 Absent 11 72 A 1/1/1 5 80/20 Example15 C-1/C-2/C-3 W-1 S-1/S-2/S-3 Absent 12 82 A 5/5/20 6 80/10/10

TABLE 3 Coating fluid for image-recording layer Acid Polymer BinderPolymerizable Polymerization Infrared Radical color-developingHydrophilic particle polymer compound initiator absorber production aidagent compound (parts) (parts) (parts) (parts) (parts) (parts) (parts)(parts) Example 16 G-16 B-1 M-4 I-1 K-2/K-3 R-1 H-2 T-1/T-2/T-3 742 98140 133 51/53 20 18 5/5/5 Example 17 G-17 B-1 M-2/M-3 I-2 K-2 R-1H-1/H-3 T-2/T-3 480 123 88/88 141 20 17 51/53 45/45 Example 18 G-18 B-1M-5 I-1/I-3 K-1 R-1 H-2/H-3 T-3 520 256 98 22/101 23 33 11/13 20 Example19 G-19 B-1 M-3/M-4 I-1 K-1 R-1 H-3 — 563 169 75/126 89 68 41 98 0Example 20 G-20 B-1 M-2/M-4 I-2/I-3 K-1/K-3 R-1 — T-1/T-2 360 153 66/138121 12/13 3 0 5/30 Example 21 G-21 B-1 M-1/M-2/M-3 I-1 K-3 R-1 H-4 T-3458 181 67/67/67 163 22 12 60 25 Comparative G′-1 B-1 M-4/M-5 I-1 K-3R-1 H-1 T-1/T-3 Example 1 468 179 146/78 132 58 57 58 20/30 ComparativeG′-2 B-1 M-3 I-1/I-2 K-3 R-1 H-4 T-2 Example 2 669 112 196 51/53 15 1123 5 Comparative G′-3 — M-3/M-4/M-5 I-2 K-2 R-1 H-3 T-3 Example 3 350 094/41/96 58 18 87 48 75 Comparative G′-4 B-1 M-1/M-4/M-5 I-2 K-1 R-1 H-4T-1/T-3 Example 4 386 151 68/120/36 201 21 5 41 10/30 Coating fluid forimage-recording layer Evaluation results Sensitization On-machineOn-machine agent Surfactant Solvent Protective developability Printingdevelopment scum (parts) (parts) (mass ratio) layer (number of pieces)resistance suppression property Example 16 C-1/C-2/C-3 W-1 S-1/S-2/S-3Absent 12 81 B 25/15/30 4 70/15/15 Example 17 C-1 — S-1/S-2/S-3 Present13 84 B 50.0 0 65/20/15 Example 18 C-2 W-1 S-1/S-2/S-3 Absent 14 82 A10.0 4 60/30/10 Example 19 C-3 W-1 S-1/S-2/S-3 Present 17 88 A 25.0 460/30/10 Example 20 C-1/C-2 W-1 S-1/S-2/S-3 Present 12 85 B 15/15 450/20/30 Example 21 C-2/C-3 W-1 S-1/S-2 Present 11 83 B 35/40 4 60/40Comparative — W-1 S-1/S-2/S-3 Absent 25 40 A Example 1 0 4 60/30/10Comparative C-1/C-2/C-3 W-1 S-1/S-2/S-3 Absent 100 pieces or more Cannotbe C Example 2 5/5/20 6 80/10/10 evaluated Comparative — — S-4/S-5Absent 30 50 B Example 3 0 0 80/20 Comparative C-1/C-2/C-3 W-1S-1/S-2/S-3 Absent 35 30 C Example 4 5/5/5 3 40/40/20

From the results of Table 2 and Table 3, it is clear that thelithographic printing plate precursor according to the embodiment of thepresent disclosure is superior to the lithographic printing plateprecursors of the comparative examples in terms of the printingresistance even in the case of using ultraviolet-curable ink.Furthermore, it is found that the lithographic printing plate precursoraccording to the embodiment of the present disclosure is favorable inboth on-machine developability and the on-machine development scumsuppression property.

In addition, the details of the respective compounds shown in Table 2and Table 3 other than the compounds described above will be describedbelow.

[Binder Polymer]

B-1: A compound having the following structure

In the formulae, the contents (suffixes on the lower right side ofparentheses) of individual constituent units represent mass ratios, anda suffix on the lower right side of the parenthesis of the ethyleneoxystructure represents the number of times of repetition.

[Polymerizable Compound]

M-1: Tris(acryloyloxyethyl)isocyanurate, NK ester A-9300, manufacturedby Shin-Nakamura Chemical Co., Ltd.

M-2: Dipentaerythritol pentaacrylate, SR-399, manufactured by SartomerJapan Inc.

M-3: Dipentaerythritol hexaacrylate, A-DPH, manufactured byShin-Nakamura Chemical Co., Ltd.

M-4: Dipentaerythritol pentaacrylate hexamethylene diisocyanate urethaneprepolymer, UA-510H, manufactured by Kyoeisha Chemical Co., Ltd.

M-5: Ethoxylated pentaerythritol tetaracrylate, ATM-4E, manufactured byShin-Nakamura Chemical Co., Ltd.

[Polymerization Initiator]

I-1 to I-3: Compounds having the following structures

In the structures, TsO⁻ represents a tosylate anion.

[Infrared Absorber]

K-1 to K-3: Compounds having the following structure

In the structures, Ph represents a phenyl group.

[Radical Production Aid]

R-1: A compound having the following structure

[Acid Color-Developing Agent]

H-1: S-205 (manufactured by Fukui Yamada Chemical Co., Ltd.)

H-2: GN-169 (manufactured by Yamamoto Chemicals Inc.)

H-3: Black-XV (manufactured by Yamamoto Chemicals Inc.)

H-4: Red-40 (manufactured by Yamamoto Chemicals Inc.)

(Hydrophilic Compound)

T-1: Tris(2-hydroxyethyl) isocyanurate

T-2: A compound having the following structure

T-3: Hydroxypropyl cellulose, Klucel M, manufactured by HerculesIncorporated

(Sensitization Agent)

C-1: A compound having the following structure

C-2: Benzyldimethyloctylammonium.PF₆ salt

C-3: A compound having the following structure

[Surfactant]

W-1: A compound having the following structure

In the structures, suffixes on the lower right side of parentheses ofindividual constituent units are content ratios (mass ratios).

[Solvent]

S-1: 2-Butanone (MEK)

S-2: 1-Methoxy-2-propanol (MFG)

S-3: Methanol

S-4: 1-Propanol

S-5: Distilled water

Examples 22 to 41 and Comparative Examples 5 to 8

<Production of Support 2>

On a 0.3 mm-thick aluminum plate (material: JIS A 1050), individualprocesses of (a) to (i) below were continuously carried out, therebycarrying out a surface treatment. Meanwhile, after each process andwater washing, liquid was drained using a nip roller.

(a) Alkali Etching Process

On the aluminum plate, an etching process was carried out by means ofspraying using an aqueous solution having a sodium hydroxideconcentration of 2.6% by mass, an aluminum ion concentration of 6.5% bymass, and a temperature of 70° C., thereby dissolving 6 g/m² of thealuminum plate. After that, the plate was washed with water by means ofspraying.

(b) Desmut Process

On the aluminum plate, a desmut process was carried out by means ofspraying using an aqueous solution having a temperature of 30° C. and anitric acid concentration of 1% by mass (including 0.5% by mass ofaluminum ions.) and then the plate was washed with water by means ofspraying. As the nitric acid aqueous solution used in the desmutprocess, a waste liquid of a step of carrying out an electrochemicalroughening process in a nitric acid aqueous solution using analternating current was used.

(c) Electrochemical Roughening Process

An electrochemical roughening process was continuously carried out usingan alternating current voltage of 60 Hz. An electrolytic solution was a10.5 g/L aqueous solution of nitric acid (including 5 g/L of aluminumions and 0.007% by mass of ammonium ions), and the liquid temperaturewas 50° C. The electrochemical roughening process was carried outthereon using an alternating current power supply waveform in which thetime TP taken for the current value to reach the peak from zero was 0.8msec and the duty ratio was 1:1, and the electrochemical rougheningprocess was carried out using a trapezoidal rectangular wave alternatingcurrent and a carbon electrode as a counter electrode. As the auxiliaryanode, ferrite was used. The current density was 30 A/dm² in terms ofthe peak value of the current, and the quantity of electricity was 220C/dm² in terms of the sum of the quantities of electricity in a case inwhich the aluminum plate was the positive electrode. Five percent of thecurrent coming from the power supply was divided into the auxiliaryanode. After that, the plate was washed with water by means of spraying.

(d) Alkali Etching Process

On the aluminum plate, an etching process was carried out at 32° C. byspraying an aqueous solution having a sodium hydroxide concentration of26% by mass, an aluminum ion concentration of 6.5% by mass, 0.25 g/m² ofthe aluminum plate was dissolved, a smut component including, as a mainbody, aluminum hydroxide generated at the time of the electrochemicalroughening process was removed, and, additionally, the edge portion ofthe generated pit was dissolved to smoothen the edge portion. Afterthat, the plate was washed with water by means of spraying.

(e) Desmut Process

A desmut process was carried out by spraying an aqueous solution havinga sulfuric acid concentration of 15% by mass of a temperature of 30° C.(including 4.5% by mass of aluminum ions) and then the plate was washedwith water by means of spraying. As the nitric acid aqueous solutionused in the desmut process, the waste liquid of the step of carrying outthe electrochemical roughening process in the nitric acid aqueoussolution using an alternating current was used.

(f) Electrochemical Roughening Process

An electrochemical roughening process was continuously carried out usingan alternating current voltage of 60 Hz. An electrolytic solution was a2.5 g/L aqueous solution of hydrochloric acid (including 5 g/L ofaluminum ions), and the temperature was 35° C. The electrochemicalroughening process was carried out thereon using an alternating currentpower supply waveform in which the time TP taken for the current valueto reach the peak from zero was 0.8 msec and the duty ratio was 1:1, andthe electrochemical roughening process was carried out using atrapezoidal rectangular wave alternating current and a carbon electrodeas a counter electrode. As the auxiliary anode, ferrite was used. Thecurrent density was 25 A/dm² in terms of the peak value of the current,and the quantity of electricity was 50 C/dm² in terms of the sum of thequantities of electricity in a case in which the aluminum plate was thepositive electrode. After that, the plate was washed with water by meansof spraying.

(g) Alkali Etching Process

On the aluminum plate, an etching process was carried out at 32° C. byspraying an aqueous solution having a sodium hydroxide concentration of26% by mass, an aluminum ion concentration of 6.5% by mass, 0.1 g/m² ofthe aluminum plate was dissolved, a smut component including, as a mainbody, aluminum hydroxide generated at the time of the electrochemicalroughening process was removed, and, additionally, the edge portion ofthe generated pit was dissolved to smoothen the edge portion. Afterthat, the plate was washed with water by means of spraying.

(h) Anodization Process

2.5 g/m² of a direct current anodized film was formed on the aluminumplate at a current density of 15 A/dm² using a 15% by mass aqueoussolution of sulfuric acid (including 0.5% by mass of aluminum ions) asan electrolytic solution, washed with water, and dried. The average porediameter of the surface layer of the anodized film (surface-average porediameter) was 10 nm.

The pore diameter of the surface layer of the anodized film was measuredusing a method in which the surface was observed an ultrahigh resolutionSEM (S-900 manufactured by Hitachi, Ltd.) at a relatively lowacceleration voltage of 12 V at a magnification of 150,000 times withoutcarrying out a vapor deposition process or the like for impartingconductive properties, 50 pores were randomly extracted, and the averagevalue was obtained. The standard deviation error was ±10% or less.

(i) Hydrophilization Process

After that, in order to ensure the hydrophilicity of a non-image area, asilicate process was carried out by dipping the aluminum plate in a 2.5%by mass aqueous solution of No. 3 sodium silicate at 50° C. for sevenseconds, and the aluminum plate was washed with water by means ofspraying, thereby producing a support 2. The attached amount of Si was11 mg/m².

As a coating fluid for an undercoat layer and a coating fluid for aprotective layer, the above-described coating fluid for an undercoatlayer and the above-described coating fluid for a protective layer wererespectively used.

<Preparation of Coating Fluid for Image-Recording Layer>

Individual components were added according to the amounts used shown inTable 4, a solvent was added thereto so that the concentration of thesolid content reached 7.0% by mass, and the components were mixedtogether. The amounts (parts) of individual materials added in Table 4are the amounts of solid contents.

Meanwhile, a coating fluid for an image-recording layer including apolymer particle was prepared by mixing and stirring a photosensitiveliquid containing components shown in Table 4 other than the polymerparticle in a mixed state and a polymer particle dispersion liquidimmediately before the application so as to obtain a composition shownin Table 4.

An expression such as “M-4/M-5 146/78” in Table 4 indicates that 146parts of a compound M-4 and 78 parts by a compound M-5 are included.

<Production of Lithographic Printing Plate Precursors>

Lithographic printing plate precursors of Examples 22 to 41 andComparative Examples 5 to 8 were respectively produced using thefollowing method.

The coating fluid for an undercoat layer having the above-describedcomposition was applied onto the support 2 so that the dried coatingamount reached 20 mg/m², thereby forming an undercoat layer. Eachcoating fluid for an image-recording layer shown in Table 4 was appliedonto the undercoat layer by means of bar coating and dried in an oven at120° C. for 40 seconds, thereby forming an image-recording layer havinga dried coating amount of 1.0 g/m².

The coating fluid for the image-recording layer was prepared by mixingand stirring the polymer particle immediately before the application.

As necessary, the coating fluid for a protective layer having theabove-described composition was applied onto the image-recording layerby means of bar coating and dried in an oven at 120° C. for 60 seconds,thereby forming a protective layer having a dried coating amount of 0.15g/m².

Examples in which the protective layer was formed have an expression of“Present” in the “Protective layer” column in Table 4.

<Evaluation of Lithographic Printing Plate Precursors>

The lithographic printing plate precursors produced as described abovewere exposed (to an equivalent irradiation energy of 110 mJ/cm²) usingMagnus 800 Quantum equipped with an infrared semiconductor lasermanufactured by Kodak Japan Ltd. under conditions of an output of 27 W,an external surface drum rotation speed of 450 rpm, and a resolution of2,400 dpi (dots per inch, 1 inch is equal to 2.54 cm). Exposed imageswere provided with a solid image and an amplitude modulation screen (AMscreen) 3% halftone dot chart.

(1) Developability

[Development Process]

A development process was carried out on the exposed lithographicprinting plates using Clean Out Unit+ C85 manufactured by Glunz & Jensenat a transportation rate of 60 cm/min and 25° C., thereby producinglithographic printing plates. In the development process, a developerhaving the following composition was used. This developer is a developercapable of carrying out the removal of the protective layer,development, and gum pulling with a single liquid.

<Developer>

-   -   PELEX NBL (sodium alkyl naphthalene sulfonate, anionic        surfactant manufactured by KAO Corporation): 7.8 parts by mass    -   NEWCOL B13 (polyoxyethylene aryl ether, nonionic surfactant        manufactured by Nippon Nyukazai Co., Ltd.): 2.0 parts by mass    -   SURFYNOL 2502 (manufactured by Air Products and Chemicals,        Inc.): 0.6 parts by mass    -   Benzyl alcohol (manufactured by Wako Pure Chemical Corporation):        0.8 parts by mass    -   Sodium gluconate (manufactured by Fuso Chemical Co., Ltd.): 3.0        parts by mass    -   Sodium hydrogen phosphate (manufactured by Wako Pure Chemical        Corporation): 0.3 parts by mass    -   Sodium hydrogen carbonate (manufactured by Wako Pure Chemical        Corporation): 0.3 parts by mass    -   Defoamer (SILCOLAPSE 432 manufactured by Bluester Silicones):        0.01 parts by mass    -   Water: 85.49 parts by mass (pH: 8.6)

The concentration in a non-exposed portion after the development processwas measured. Regarding the measurement of the concentration, the cyanconcentration was measured using a spectrophotometer (SpectroEyemanufactured by X-Rite, Incorporated). The difference (ΔD) between theobtained value of the cyan concentration and the value of the cyanconcentration of the support 2 on which the application was not carriedout was computed, and the developability was evaluated as A to C. As ΔDdecreases, the area of the image-recording layer remaining in thenon-image area after the development process becomes smaller, and thedevelopability is more favorable.

A: ΔD≤0.01

B: 0.01<ΔD≤0.03

C: 0.03<ΔD

(2) Printing Resistance

The lithographic printing plate obtained by the development process wasattached to a cylinder of a medium octavo paper-size printer SX-74manufactured by Heidelberger Druckmaschinen AG without being developed.To the present printer, a 100 L-capacity dampening water circulationtank having a non-woven fabric filter and a temperature control devicewas connected. Dampening water (80 L) containing 2.0% of dampening waterS-Z1 (manufactured by Fujifilm Corporation) was prepared in acirculation device, T&K UV OFS K-HS black GE-M (manufactured by T&K TOKACo., Ltd.) was used as printing ink, dampening water and ink weresupplied using a standard automatic printing start method, and thenprinting was carried out on 500 pieces of TOKUBISHI art paper (76.5 kg)at a printing rate of 10,000 pieces per hour. As the number of pieces ofprinted paper increased, the image area gradually wore, and thus the inkdensity on printed matters decreased. The number of pieces of paperprinted until the value of the halftone dot area ratio of AM screen 3%halftone dots on a printed matter measured using a gretag density meter(manufactured by GretagMacbeth) decreased to be 1% lower than themeasurement value obtained from the 500^(th) piece of printed paper wasused as the number of pieces of completely printed paper to evaluate theprinting resistance. The printing resistance was evaluated usingrelative printing resistance for which the value obtained in a case inwhich the number of pieces of printed paper reached 50,000 wasconsidered as 100. As the numerical value increase, the printingresistance becomes more favorable. The evaluation results are shown inTable 4. In Table 4, an expression of “Cannot be evaluated” indicatesthat the development of the lithographic printing plate precursor wasnot possible and the evaluation of the printing resistance was notpossible.

Relative printing resistance=(number of pieces of printed paper ofsubject lithographic printing plate precursor)/50,000×100

TABLE 4 Coating fluid for image-recording layer PolymerizablePolymerization Radical Polymer particle Binder polymer compoundinitiator Infrared absorber production aid Coloring agent (parts)(parts) (parts) (parts) (parts) (parts) (parts) Example 22 G-1 B-1M-4/M-5 I-1 K-3 R-1 S-1 468 179 146/78 132 58 57 20 Example 23 G-2 B-1M-1/64-2 I-1 K-1 R-1 S-1 453 156 123/101 135 50 49 20 Example 24 G-3 B-1M-1/M-2 I-1 K-1 R-1 S-1 453 156 123/101 135 50 49 20 Example 25 G-4 B-1M-2/M-3/M-4 I-1 K-1 R-1 S-1 556 181 77/75/69 125 53 51 20 Example 26 G-5B-1 M-2/M-3/M-4 I-1 K-1 R-1 S-1 556 181 77/75/69 125 53 51 20 Example 27G-6 B-1 M-2/M-3/M-4 I-1 K-1 R-1 S-1 556 181 77/75/69 125 53 51 20Example 28 G-7 — M-3/M-4/M-5 I-2 K-2 R-1 S-1 350 0 94/41/96 58 18 87 20Example 29 G-8 B-1 M-1/M-5 I-3 K-3 R-1 S-1 489 163 88/103 125 49 60 20Example 30 G-9 B-1 M-1/M-5 I-3 K-3 R-1 S-1 489 163 88/103 125 49 60 20Example 31 G-10 B-1 M-1/M-5 I-3 K-3 R-1 S-1 489 163 88/103 125 49 60 20Example 32 G-11 B-1 M-1/M-5 I-3 K-3 R-1 S-1 489 163 88/103 125 49 60 20Example 33 G-12 B-1 M-1/M-4/M-5 I-2 K-1 R-1 S-1 386 151 68/120/36 201 215 20 Example 34 G-13 B-1 M-1 I-1 K-1/K-2 R-1 S-1 241 213 213 151 25/25 920 Example 35 G-14 B-1 M-2 I-2 K-2 — S-1 190 165 253 178 89 0.0 20Example 36 G-15 B-1 M-3 I-1/I-2 K-3 R-1 S-1 669 112 196 51/53 15 11 20Example 37 G-16 B-1 M-4 I-1 K-2/K-3 R-1 S-1 742 98 140 133 51/53 20 20Example 38 G-17 B-1 M-2/M-3 I-2 K-2 R-1 S-1 480 123 88/88 141 20 17 20Example 39 G-18 B-1 M-5 I-1/I-3 K-1 R-1 S-1 520 256 98 22/101 23 33 20Example 40 G-19 B-1 M-3/M-4 I-1 K-1 R-1 S-1 563 169 75/126 89 68 41 20Example 41 G-21 B-1 M-1/M-2/M-3 I-1 K-3 R-1 S-1 458 181 67/67/67 163 2212 20 Comparative G′-1 B-1 M-1/M-5 I-1 K-3 R-1 S-1 Example 5 468 179146/78 132 58 57 20 Comparative G′-2 B-1 M-3 I-1/I-2 K-3 R-1 S-1 Example6 669 112 196 51/53 15 11 20 Comparative G′-3 — M-3/M-4/M-5 I-2 K-2 R-1S-1 Example 7 350 0 94/41/96 58 18 87 20 Comparative G′-4 B-1M-1/M-4/M-5 I-2 K-1 R-1 S-1 Example 8 386 151 68/120/36 201 21 5 20Coating fluid for image-recording layer Evaluation results Hydrophiliccompound Sensitization agent Surfactant Solvent Printing (parts) (parts)(parts) (mass ratio) Protective layer Developability resistance Example22 T-1/T-3 — W-1 S-1/S-2/S-3 Absent A 85 20/30 0 4 60/30/10 Example 23T-1 C-1/C-2/C-3 W-1 S-1/S-2/S-3 Present A 82 20 25/23/30 4 50/40/10Example 24 T-1 C-1/C-2/C-3 W-1 S-1/S-2/S-3 Present A 74 20 25/23/30 450/40/10 Example 25 T-1/T-3 C-1/C-3 W-1 S-1/S-2/S-3 Present A 80 15/3027/27 4 55/30/15 Example 26 T-1/T-3 C-1/C-3 W-1 S-1/S-2/S-3 Present A 7615/30 27/27 4 55/30/15 Example 27 T-1/T-3 C-1/C-3 W-1 S-1/S-2/S-3Present A 72 15/30 27/27 4 55/30/15 Example 28 T-3 — — S-4/S-5 Absent A73 75 0 0 80/20 Example 29 T-1/T-2/T-3 C-1/C-2/C-3 W-1 S-1/S-2/S-3Present A 83 10/10/10 15/13/25 4 70/20/10 Example 30 T-1/T-2/T-3C-1/C-2/C-3 W-1 S-1/S-2/S-3 Present A 78 10/10/10 15/13/25 4 70/20/10Example 31 T-1/T-2/T-3 C-1/C-2/C-3 W-1 S-1/S-2/S-3 Present A 75 10/10/1015/13/25 4 70/20/10 Example 32 T-1/T-2/T-3 C-1/C-2/C-3 W-1 S-1/S-2/S-3Present A 71 10/10/10 15/13/25 4 70/20/10 Example 33 T-1/T-3 C-1/C-2/C-3W-1 S-1/S-2/S-3 Absent A 68 10/30 5/5/5 3 40/40/20 Example 34 T-1/T-3 —W-1 S-1/S-2/S-3 Present A 81 10/25 0 2 40/30/30 Example 35 T-1/T-3C-1/C-2/C-3 W-1 S-1/S-3 Absent A 67 20/20 1/1/1 5 80/20 Example 36 T-2C-1/C-2/C-3 W-1 S-1/S-2/S-3 Absent A 77 5 5/5/20 6 80/10/10 Example 37T-1/T-2/T-3 C-1/C-2/C-3 W-1 S-1/S-2/S-3 Absent A 76 5/5/5 20/15/30 470/15/15 Example 38 T-2/T-3 C-1 — S-1/S-2/S-3 Present A 79 45/45 50.0 065/20/15 Example 39 T-3 C-2 W-1 S-1/S-2/S-3 Absent A 77 20 10.0 460/30/10 Example 40 — C-3 W-1 S-1/S-2/S-3 Present A 83 0 25.0 4 60/30/10Example 41 T-3 C-2/C-3 W-1 S-1/S-2 Present A 78 25 35/40 4 60/40Comparative T-1/T-3 — W-1 S-1/S-2/S-3 Absent A 35 Example 5 20/30 0 460/30/10 Comparative T-2 C-1/C-2/C-3 W-1 S-1/S-2/S-3 Absent C Cannot beExample 6 5 5/5/5 6 80/10/10 evaluated Comparative T-3 — — S-4/S-5Absent B 45 Example 7 75 0 0 80/20 Comparative T-1/T-3 C-1/C-2/C-3 W-1S-1/S-2/S-3 Absent B 25 Example 8 10/30 5/5/5 3 40/40/20

From the results of Table 4, it is clear that the lithographic printingplate precursor according to the embodiment of the present disclosure issuperior to the lithographic printing plate precursors of thecomparative examples in terms of the printing resistance even in thecase of using ultraviolet-curable ink. Furthermore, it is found that thelithographic printing plate precursor according to the embodiment of thepresent disclosure is favorable in terms of developability.

In addition, the details of the respective compounds shown in Table 4other than the compounds described above will be described below.

[Coloring Agent]

S-1 (the Following Structure)

The disclosure of JP2017-108002 filed on May 31, 2017 and the disclosureof JP2017-210126 filed on Oct. 31, 2017 are all incorporated into thepresent specification by reference.

All of documents, patent applications, and technical standards describedin the present specification are incorporated into the presentspecification by reference to approximately the same extent as a casewhere it is specifically and respectively described that the respectivedocuments, patent applications, and technical standards are incorporatedby reference.

What is claimed is:
 1. A lithographic printing plate precursorcomprising: an image-recording layer on a hydrophilic support, whereinthe image-recording layer includes a polymer particle including anaddition polymerization-type resin having a hydrophilic structure and acrosslinking structure, an infrared absorber, a polymerizationinitiator, a polymerizable compound, and a radical production aid. 2.The lithographic printing plate precursor according to claim 1, whereinthe addition polymerization-type resin has an ionic group or an acidradical as the hydrophilic structure.
 3. The lithographic printing plateprecursor according to claim 1, wherein the addition polymerization-typeresin has a sulfonate group or a sulfonic acid group as the hydrophilicstructure.
 4. The lithographic printing plate precursor according toclaim 1, wherein the addition polymerization-type resin has apolyalkylene oxide structure as the hydrophilic structure.
 5. Thelithographic printing plate precursor according to claim 1, wherein theaddition polymerization-type resin has a group represented by Formula Zas a group having the hydrophilic structure,-Q-W—Y  Formula Z in Formula Z, Q represents a divalent linking group, Wrepresents a divalent group having a hydrophilic structure or a divalentgroup having a hydrophobic structure, Y represents a monovalent grouphaving a hydrophilic structure or a monovalent group having ahydrophobic structure; here, any of W and Y has a hydrophilic structure.6. The lithographic printing plate precursor according to claim 1,wherein the crosslinking structure includes at least one constituentunit selected from the group consisting of constituent units representedby BR-1 to BR-16,

in the structure, R^(BR) each independently represent a hydrogen atom ora methyl group, and n represents an integer of 1 to
 20. 7. Thelithographic printing plate precursor according to claim 1, wherein theimage-recording layer further includes a binder polymer.
 8. Thelithographic printing plate precursor according to claim 1, furthercomprising: a protective layer on the image-recording layer.
 9. Thelithographic printing plate precursor according to claim 8, wherein theprotective layer includes an inorganic lamellar compound.
 10. Thelithographic printing plate precursor according to claim 1, wherein anon-exposed portion of the image-recording layer can be removed by atleast any of dampening water or printing ink.
 11. A method for producinga lithographic printing plate comprising: exposing the lithographicprinting plate precursor according to claim 1 in an image shape andforming an exposed portion and a non-exposed portion; and removing thenon-exposed portion by supplying at least one of printing ink ordampening water.
 12. A method for producing a lithographic printingplate comprising: exposing the lithographic printing plate precursoraccording to claim 1 in an image shape and forming an exposed portionand a non-exposed portion; and removing the non-exposed portion bysupplying a developer having a pH of 2 or higher and 11 or lower.